1. A friction drive belt comprising a compression rubber layer which is provided on an inner periphery of a belt body and transmits power between pulleys upon coming into contact with the pulleys, wherein the compression rubber layer includes a surface rubber layer having numerous pores, of which an average pore size is 80 to 120 μm, on a pulley contact surface, and an inner rubber layer which is provided toward an inside of the belt relative to the surface rubber layer, the inner rubber layer has storage modulus at 25° C. in a belt length direction higher than that of the surface rubber layer and is in the range from 30 to 50 MPa.