A scooter comprising: a vehicle body frame; a front wheel; a foot board at least partially disposed rearward of the front wheel, the foot board being supported by the vehicle body frame; an under cover at least partially disposed below the foot board and rearward of the front wheel; a pivot shaft disposed on the vehicle body frame; and an engine unit at least partially disposed below the foot board, the engine unit being swingably supported by the pivot shaft, wherein the engine unit has a crankcase, a cylinder body connected to the crankcase, and an exhaust port configured to emit exhaust gas, and includes a cylinder head connected to the cylinder body, the scooter includes a first exhaust pipe connected to the exhaust port of the cylinder head, a second exhaust pipe disposed downstream of the first exhaust pipe in a flow direction of an exhaust gas, a catalyst disposed between the first exhaust pipe and the second exhaust pipe and below the engine unit, a silencer connected to the second exhaust pipe and disposed rearward of the second exhaust pipe, and an oxygen sensor attached to a portion of the first exhaust pipe closer to the catalyst than an intermediate position of the first exhaust pipe, and the oxygen sensor including a portion located inside the first exhaust pipe and a portion located outside the first exhaust pipe, the portion of the oxygen sensor located outside the first exhaust pipe is disposed above a lower end of the first exhaust pipe, at least a portion of the catalyst overlaps the engine unit in a vehicle bottom view, the oxygen sensor is disposed rearward of the pivot shaft and rearward of the cylinder body, and the oxygen sensor and the under cover do not overlap each other in a vehicle bottom view, and overlap each other in a vehicle front view, characterized in that the oxygen sensor is exposed in a vehicle side view, and the oxygen sensor overlaps the crankcase in a vehicle bottom view. a vehicle body frame; a front wheel; a foot board at least partially disposed rearward of the front wheel, the foot board being supported by the vehicle body frame; an under cover at least partially disposed below the foot board and rearward of the front wheel; a pivot shaft disposed on the vehicle body frame; and an engine unit at least partially disposed below the foot board, the engine unit being swingably supported by the pivot shaft, wherein the engine unit has a crankcase, a cylinder body connected to the crankcase, and an exhaust port configured to emit exhaust gas, and includes a cylinder head connected to the cylinder body, the scooter includes a first exhaust pipe connected to the exhaust port of the cylinder head, a second exhaust pipe disposed downstream of the first exhaust pipe in a flow direction of an exhaust gas, a catalyst disposed between the first exhaust pipe and the second exhaust pipe and below the engine unit, a silencer connected to the second exhaust pipe and disposed rearward of the second exhaust pipe, and an oxygen sensor attached to a portion of the first exhaust pipe closer to the catalyst than an intermediate position of the first exhaust pipe, and the oxygen sensor including a portion located inside the first exhaust pipe and a portion located outside the first exhaust pipe, a first exhaust pipe connected to the exhaust port of the cylinder head, a second exhaust pipe disposed downstream of the first exhaust pipe in a flow direction of an exhaust gas, a catalyst disposed between the first exhaust pipe and the second exhaust pipe and below the engine unit, a silencer connected to the second exhaust pipe and disposed rearward of the second exhaust pipe, and an oxygen sensor attached to a portion of the first exhaust pipe closer to the catalyst than an intermediate position of the first exhaust pipe, and the oxygen sensor including a portion located inside the first exhaust pipe and a portion located outside the first exhaust pipe, the portion of the oxygen sensor located outside the first exhaust pipe is disposed above a lower end of the first exhaust pipe, at least a portion of the catalyst overlaps the engine unit in a vehicle bottom view, the oxygen sensor is disposed rearward of the pivot shaft and rearward of the cylinder body, and the oxygen sensor and the under cover do not overlap each other in a vehicle bottom view, and overlap each other in a vehicle front view, characterized in that the oxygen sensor is exposed in a vehicle side view, and the oxygen sensor overlaps the crankcase in a vehicle bottom view.