To provide a marine-gear apparatus which transmits a rotational power from a main engine mounted in a ship to a propeller, and reduces an operation force necessary for manually operating a forward/backward operation tool for switching a forward/backward switching mechanism, and prevents a possibility of failure in a case of water immersion.

A marine-gear apparatus 21 includes: an input shaft 23 to which a rotational power from a main engine 20 is inputted; a forward/backward switching mechanism for switching the rotational power of the input shaft 23 to an output for one of a forward moving, a neutral, and a reverse rotation; an output shaft 25 transmitting the output from the forward/backward switching mechanism to a propeller; and an electrically-drive type actuator 50 which switches the forward/backward switching mechanism in association with an operation of a forward/backward operation tool. The electrically-drive type actuator 50 is provided in a gear case 22 accommodating the input shaft 23, the output shaft 25, and the forward/backward switching mechanism. A main body 51 of the electrically-drive type actuator 50 is positioned above a shaft center line CL of the output shaft 25.