There is provided a seat opening/closing structure for a saddle riding vehicle that suppresses the cost and simplifies the structure to enhance usability. A seat hinge 31 has a vehicle-body-side hinge 51A provided to a vehicle body side, and a seat-side hinge 52 which is turnably secured to the vehicle-body-side hinge 51A through a hinge pin 55. The seat-side hinge 52 has a projecting portion 52h extending to the vehicle-body-side hinge 51A, the vehicle-body-side hinge 51A is provided with a leaf spring 64 having a top portion 64a with which the projecting portion 52h can come into contact, and the projecting portion 52h gets over the top portion 64a of the leaf spring 64 when the seat is opened, whereby the seat-side hinge 52 is supported by the leaf spring 64 and the seat is kept under an open state.