An opening and closing apparatus of an opening and closing member includes a support member including a first support wall portion and a second support wall portion, a support pin including axially opposed end portions, a pulley arranged between the first and second support wall portions, a transmission belt engaged at the pulley, and an electric drive source moving the transmission belt. The first support wall portion includes a penetration bore into which one of the axially opposed end portions of the support pin is inserted to be positioned and a slit continuously provided to the insertion bore. An engagement portion is provided at an axial tip end of the support pin, the engagement portion including a step engageable with a peripheral edge portion of the penetration bore and a tapered portion connected to the step and reduced in diameter towards a tip end of the engagement portion.