Mont St Michel交通問題

TGV (fast train) from Paris Montparnasse to Rennes (2 hours, cost between 25-51 EUR)
The bus costs about €11.
For more details, you can visit the below links.
http://www.francetravelguide.com/getting-from-paris-to-mont-saint-michel.html
You can buy TGV ticket at train station and buy bus ticket on the bus.