Oil filler cap and saddle riding type vehicle

An oil filler cap comprising:

• a cap body that is screwed to an oil filler opening part of a fuel tank and that closes an oil filler opening;
• a ventilation passage part that penetrates through the cap body and that allows an inside and an outside of the fuel tank to communicate with each other;
• a valve device that operates a float in accordance with a fuel fluid-level position and that opens and closes an opening which communicates with the ventilation passage part;
• a grip part that is provided to be relatively rotatable around a screw axis with respect to the cap body;
• and
• a ratchet mechanism that is formed between the grip part and the cap body and that monitors a tightening torque of the cap body,
• wherein a valve part of the valve device is arranged between a lower end of a screw part that is screwed to the oil filler opening part in the cap body and a seal surface that is arranged at a higher position than the screw part, the ventilation passage part is arranged above the valve part, and the ratchet mechanism is arranged on an outer circumferential side of the ventilation passage part,
• the ventilation passage part penetrates through a portion of the cap body including a center axis of the cap body and a portion of the grip part including a center axis of the grip part along the screw axis and is supported relatively rotatably via a seal member by a penetration part of the cap body penetrating the portion of the cap body including the center axis of the cap body,
• the seal member and the ratchet mechanism overlap in a direction of the screw axis, and
• the ratchet mechanism is arranged on an outer circumferential side of an outer circumferential end of the seal member.