A locking device for a canister-type thruster is disclosed. The locking device for a canister-type thruster according to an embodiment of the present invention comprises: a canister lifted inside a trunk of a hull or a floating structure; a thruster arranged in the lower part of the canister to be lifted with the canister; and a locking device for locking the canister in the trunk. The locking device comprises: held rods horizontally protruding from the outer surface of the canister to be held; and multiple holding members fixed on the inner surface of the trunk, and arranged in relevant positions to hold the held rods. The multiple holding members include first holding members having a holding groove in which each held rod is inserted when the thruster is positioned below the bottom surface of the hull; and second holding members on which the held rods are placed in a state where the thruster is entered into the trunk. The bottom surface of the first holding members is opened. The top of the holding grooves is inclined downward toward the inner surface of the trunk. The top of the held rods is inclined downward toward the inner surface of the trunk corresponding to the shape of the holding grooves to be inserted in the holding grooves of the first holding members.
