A guide mechanism, which guides a slider along an inner wall surface of a frame, includes a plurality of resin sliding members retained by the slider. The plurality of resin sliding members include a pair of first resin sliding members that make sliding movement along first sliding grooves formed in a bottom wall section of the frame, a pair of second resin sliding members that make sliding movement along second sliding grooves formed in side wall sections of the frame, and a pair of third resin sliding members that make sliding movement along third sliding grooves formed in the side wall sections.