A vehicular sliding door structure includes a sliding door having a closure portion configured to undergo abutting engagement with a mating portion of a vehicle body. The closure portion has an opening for allowing the entry of a striker therethrough into an internal space of the sliding door for locking engagement with a lock device. An anti-pinch sensor disposed on the closure portion has a sensor harness arranged to enter an internal space of the sliding door through the opening. A single cover member is provided on the closure portion so as to close the opening and cover a portion of the sensor harness. The cover member has a through-hole for the passage therethrough of the striker.