An electromagnetically actuated bicycle trainer includes a base, a support assembly disposed on the base, and a hysteresis resistance generating module. The support assembly includes a support arm, and a fastening member disposed on the support arm and for securing an axle of a pedaling wheel. The hysteresis resistance generating module includes an inner magnetic stationary member and an outer magnetic stationary member, a semi-hard magnetic rotating member between the inner magnetic stationary member and the outer magnetic stationary member, and a conductive coil. The conductive coil receives an electric power and senses opposite magnetisms that the inner magnetic stationary member and the outer magnetic stationary member generate. Thus, the semi-hard magnetic rotating member is caused to generate a hysteresis resistance when rotated in response to hysteresis effects.