A gear mechanism, including: a first gear; and a second gear. The first gear and the second gear are arranged at an inclination angle to form a first meshing region and a second meshing region. Multiple tooth tip portions of the first gear and multiple tooth tip portions of the second gear are each formed to be held in contact with each other at one point in the first meshing region. Multiple recessed portions of the first gear and multiple recessed portions of the second gear are each formed to conform to a passing region extending along movement of one of the multiple mating tooth tip portions at the time of moving in the second meshing region.