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.

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 electrically-drive type direct drive actuator 50 having a rod 52 which proceeds or recedes in association with an operation of a forward/backward operation tool; and an actuation body 46 which switches the forward/backward switching mechanism into one of a forward moving state, a neutral state, and a backward moving state by a rotation movement. The electrically-drive type direct drive actuator 50 and the actuation body 46 are connected to each other via a conversion mechanism 53 for converting a proceeding/receding movement of the rod 52 into a rotation movement of the actuation body 46.