A pneumatic tire including a longitudinal main groove formed concavely on a tread surface thereof in a radial direction thereof by extending the longitudinal main groove linearly in a circumferential direction thereof; and narrow grooves formed concavely on at least an outer side surface of both side surfaces of the longitudinal main groove opposed to each other in a widthwise direction of the pneumatic tire by spacing the narrow grooves at certain intervals in a circumferential direction of the pneumatic tire. Each of the narrow grooves is so configured that a longer side of each of the narrow grooves extends in the radial direction of the pneumatic tire and that a shorter side of each of the narrow grooves extends in the circumferential direction of the pneumatic tire. A sectional configuration of a position having a maximum sectional area in each of the narrow grooves is circular arc-shaped.