To provide a resin cap which prevents a fragment of a flap from mixing into contents of a bottle.

The resin cap 1 comprises a top plate 2, a cylindrical skirt 4 hanging from the top plate 2 and having a female spiral on an inner periphery, and a pilferproof band 7 provided at an end of the skirt 4 via a weakened line 6 continuously extending to make a round along an inner peripheral surface thereof and equipped with a flap piece 9 protruding from a base 8 which is a joint with the inner peripheral surface radially inward and slantly upward. The pilferproof band 7 is formed with a score 17 so that its upper end reaches the weakened line 6 while a remaining portion 16 which can be torn by predetermined shearing force between its lower end and a lower rim of the band 7 is left. In addition, a portion of the flap 9 corresponding to the score 17 is cut.