The present invention relates to a power transmission belt provided with a tension member, a tension member-supporting layer, a tension rubber layer, and a compression rubber layer, the belt having a plurality of cog portions, in which the tension member is formed of an aramid fiber, the compression rubber layer is formed of a vulcanized rubber composition containing a rubber component and aramid short fibers embedded in the vulcanized rubber composition with being arranged in a width direction of the belt, the power transmission belt has a strain of from 0.5 to 0.8% when compressed under a stress of 2.0 N/mm2 in the width direction, and the power transmission belt has a strain of from 0.35 to 0.7% when pulled under a load of 2 kN in the lengthwise direction.