A pneumatic tire for a motorcycle, having a pair of bead portions, a pair of sidewall portions continuous with the bead portions, a tread provided to extend in a toroidal shape across the pair of sidewall portions, and a directional pattern provided at the tread specifying a rotation direction such that grooves extend, in the rotation direction, toward the outer side in a tread width direction; comprising: a main groove in a bent shape, constituted of a first groove part extending substantially in a tread circumferential direction within a ground contact region in straight running, of a ground contact surface of the tread, and a second groove part extending from the outer end portion of the first groove part, the outer end portion of the first groove part being outer in the tread width direction, the second groove part extending in the rotation direction specified by the directional pattern toward the outer side in the tread width direction slantly with respect to the specified rotation direction; and an auxiliary groove formed at a position on the outer side in the tread width direction of the second groove part and distanced in the tread circumferential direction from the outer end portion of the second groove part, the outer end portion of the second groove part being outer in the tread width direction, such that the auxiliary groove extends, in the rotation direction, toward the outer side in the tread width direction slantly with respect to the specified rotation direction, wherein, provided that a groove width of the main groove at a connection portion of the first groove part and the second groove part is A (mm), a groove width of the second groove part at an end on the outer side in the tread width direction is B (mm), and a groove width of the auxiliary groove is C (mm), A > B ≥ C. a main groove in a bent shape, constituted of a first groove part extending substantially in a tread circumferential direction within a ground contact region in straight running, of a ground contact surface of the tread, and a second groove part extending from the outer end portion of the first groove part, the outer end portion of the first groove part being outer in the tread width direction, the second groove part extending in the rotation direction specified by the directional pattern toward the outer side in the tread width direction slantly with respect to the specified rotation direction; and an auxiliary groove formed at a position on the outer side in the tread width direction of the second groove part and distanced in the tread circumferential direction from the outer end portion of the second groove part, the outer end portion of the second groove part being outer in the tread width direction, such that the auxiliary groove extends, in the rotation direction, toward the outer side in the tread width direction slantly with respect to the specified rotation direction, wherein, provided that a groove width of the main groove at a connection portion of the first groove part and the second groove part is A (mm), a groove width of the second groove part at an end on the outer side in the tread width direction is B (mm), and a groove width of the auxiliary groove is C (mm), A > B ≥ C.