An electric variable inertia apparatus uses a servo drive device to drive a planetary gear mechanism to which a load assembly is attached to provide variable and wide-ranging rotational inertia. A planetary frame and a ring gear of the planetary gear mechanism act as two input ends of the electric variable inertia apparatus, and a rotated shaft of a sun gear assembly of the planetary gear mechanism acts as a load terminal. The load assembly is rotated at a controlled rotational velocity with the ring gear to generate a widely ranging rotational inertia to change a dissipating degree of an input energy from the planetary frame. The electric variable inertia apparatus can be used in different fields such as shock absorbers, stabilizers, dampers or vibrators in the automotive field, etc.