In an opening/closing mechanism of a sunroof apparatus, an engaged portion engaged with a cam groove smoothly slides on upper and lower cam surfaces of a cam groove, and stiffness to support a roof panel is increased at low costs. The engaged portion includes a first sliding portion having a convex curve facing upward and sliding on the upper cam surface of the cam groove, and a second sliding portion coupled to the first sliding portion at a front or a rear of a vehicle, having a convex curve facing downward, and sliding on the lower cam surface of the cam groove.