In a rotation drive device (10), each of rotating units (20) has a swing arm (23) which is supported so as to be swingable around a swing center axis (23A) provided in a support table (22), a weight (24) is provided at a position at which a length of an arm from the swing center axis (23A) of the swing arm (23) is longer, and a connection point in a fluid cylinder (25) side is provided at a position at which the length of the arm from the swing center axis (23A) is shorter.