Saint Michel RER Station Steps

I don't know about the main station on the left bank but the exit onto the island, just down from Notre Dame, has a very narrow up only escalator at one end and stairs at the other.

I'm thinking the B Line is the bottom of three and there's escalators and an elevator down in there somewhere.

But the last bit to ground level is regular steps if you use the two exits on the sidewalk between the road and the river.

If there's something else that comes out across the street, I don't know about it.

Roxxane.. if you really can't lug your bags up do be careful. I have seen many an escalator out of order in my years of visiting Paris. If you would hope for an escalator but could manage the stairs then fine.. but really if you absolutely could not manage.. don't risk it.. or pack lighter!!! Paris seems to have stairs everywhere.. I have stayed in hotels with elevators.. but there were steps to get to elevator level.. or elevators but they put you on a floor thats still leaves you walking up a flight or 1/2 flight of stairs to get to your room ( obviously these weren't four stars.. but good reputable budget -moderate places)
I even got "upgraded" in a hotel once to a "duplex" room ... but the room had the bathroom on a second level that was up the steepest stairs( almost a ladder!) I have ever seen. I managed fine but know many would have had trouble.

Pack light or take a taxi!

I actually did some on-site "research" on this very question in January. I was traveling "heavy" and wanted to get to the airport without lugging bags up and down station stairs. I crossed St Michel station off my list. Almost no Metro/RER stations have elevators or escalators to the street level except at actual train stations.
You can get to street level at Les Halles and Port Royal on the RER B using escalators and/or elevators. Take a taxi from there if you have issues with hauling bags up steps.

Bus No. 350 will take you from CDG to Gare de l'est for 3 bus tickets (about 5 euro) and then you could grab a taxi. Cheap n easy.

the choice to take heavy bags is a choice to taxi from the airport -- or take a bus and some cobbled together patch of taxis

travel light and avoid this if you can

I just learned of an elevator at the Saint-Michel RER B station. Get on one of the middle cars of the train leaving Charles de Gaulle Airport to be closest to this exit. When you get off the train at Saint-Michel, walk to the center of the platform and follow the signs to "Sortie-6", an elevator that will take you directly to street level. There is a dedicated turnstile on the RER-B platform for the elevator, and you must use your ticket to exit here. The elevator has been in service since 2009. It surfaces at the corner of Quai St-Michel and rue Xavier Privas on the left bank with a nice welcoming view of the Notre Dame towers. You can also enter here for your return trip if you have your train tickets already. There are no ticket booths or kiosks at this entrance.

@Sam, What about the Luxembourg RER station. Is there an Escalator there?

@ Bets I used that station several times and there is an escalator, I just can't remember if it is all the way to street level. You only really notice when you're schlepping a load. I do know that there is an elevator at the Port Royal station.