A drive device comprises a housing, a drive portion, a spindle member to rotate by driving of the drive portion, a nut member screwed with the spindle member); a moving member coupled to the nut member, and a rotation regulating portion which suppresses rotation of the nut member to move the nut member) in an axis X direction of the spindle member, wherein the moving member has a fragile portion to be broken by a predetermined force being weaker than a force required to break the nut member, and the fragile portion is configured that a fracture portion with which the nut member is pressable by the moving member toward the drive portion is formable when the fragile portion is broken.