A fixing device for vehicle doors includes a door lock striker, a fixed member, and a movable member. The fixed member has two inclined surfaces that are movable relative to the door lock striker and located on opposite sides of the door lock striker. The movable member has two inclined surfaces arranged on opposite sides of the door lock striker and is urged such that each inclined surface is pushed against the corresponding inclined surface of the fixed member. The door lock striker includes a leg portion. The movable member includes two bodies forming the two inclined surfaces of the movable member, and a connecting portion that connects the bodies at the rear end portions of the bodies, which are pressed towards the fixed member and moved rearward. The connecting portion has an arched shape that protrudes in the protruding direction of the leg portion.