A marine propulsion device controller for starting/stopping an engine provided in each of a plurality of propulsion devices, the marine propulsion device controller comprising: an operation unit configured to output a start command for starting all engines of the plurality of propulsion devices collectively; and a start control unit (60L,60C,60R) configured to start in response to receiving a first operation on the operation unit and start all the engines of the plurality of propulsion devices collectively in response to receiving the start command in an activated state, wherein the operation unit is provided in common for the plurality of propulsion devices, and is capable of receiving the first operation and receiving a second operation in a state where the first operation has been received, and also capable of receiving the second operation consecutively after the first operation is received, and the operation unit is configured to output the start command in response to receiving the second operation, wherein each of a plurality of the start control units (60L,60C,60R) is provided corresponding to each of the plurality of propulsion devices, characterized in that the operation unit is configured to output the start command to a representative start control unit among all the start control units (60L,60C,60R) corresponding to the plurality of propulsion devices, the representative start control unit is configured to start a corresponding engine in response to receiving the start command from the operation unit, and is configured to transfer the start command to the other start control units (60C,60R) among all the start control units (60L,60C,60R), and each of the other start control units (60C,60R) is configured to start the corresponding engine in response to receiving the transferred start command. an operation unit configured to output a start command for starting all engines of the plurality of propulsion devices collectively; and a start control unit (60L,60C,60R) configured to start in response to receiving a first operation on the operation unit and start all the engines of the plurality of propulsion devices collectively in response to receiving the start command in an activated state, wherein the operation unit is provided in common for the plurality of propulsion devices, and is capable of receiving the first operation and receiving a second operation in a state where the first operation has been received, and also capable of receiving the second operation consecutively after the first operation is received, and the operation unit is configured to output the start command in response to receiving the second operation, wherein each of a plurality of the start control units (60L,60C,60R) is provided corresponding to each of the plurality of propulsion devices, characterized in that the operation unit is configured to output the start command to a representative start control unit among all the start control units (60L,60C,60R) corresponding to the plurality of propulsion devices, the representative start control unit is configured to start a corresponding engine in response to receiving the start command from the operation unit, and is configured to transfer the start command to the other start control units (60C,60R) among all the start control units (60L,60C,60R), and each of the other start control units (60C,60R) is configured to start the corresponding engine in response to receiving the transferred start command.