To achieve a variable-pitch propeller solving a problem of structure complexity and weight increase in regard to conventional variable-pitch propellers and suitable for radio-controlled airplanes for hobby and ultralight airplanes etc.

A pitch changing axis is positioned in a front edge side by a distance of w from a pressure center O point of aerodynamic resultant force of a blade 130, and applies an aerodynamic moment reducing a blade angle to the blade 130. A rotation suppressing part 140 applies, to the blade 130, a mechanical moment increased in accordance with reduction amount of the blade angle by a function of a coil spring 150 inside a cylinder 141. During cruise flight (a), a small mechanical moment Mmc is balanced with a small aerodynamic moment Mac, leading to a large blade angle βc. During climb (b), a large mechanical moment Mmh is balanced with a large aerodynamic moment Mah, leading to a small blade angle βh.