A ship maneuvering device comprising: an engine; an outdrive device having a propeller rotated by power of the engine; a clutch selectively engaging for making a power transmission from the engine to the propeller or disengaging for cutting off the power transmission from the engine to the propeller; an operation means actuating the outdrive device; and a control device connected to the engine, the clutch and the operation means, wherein the control device stores a duty ratio, a baseline operation amount (Ms) of the operation means, and a baseline increase amount (ΔMs) of an operation amount of the operation means, wherein the duty ratio is set as a ratio of a time of engaging the clutch to a predetermined cycle, wherein the control device has a very low speed sailing mode, wherein the control device is connected to a determination means determining whether the very low speed sailing mode is executed or not, and wherein in a case in which execution of the very low speed sailing mode is determined, when the operation amount of the operation means is not more than the baseline operation amount (Ms), the control device makes a rotation speed of the engine be a low idling rotation speed (Nlow) and changes the duty ratio in a range not more than 100%, correspondingly to the operation amount of the operation means, characterized in that when the operation amount of the operation means excesses the baseline operation amount (Ms), and an increase amount (ΔM) of the operation amount from the baseline operation amount (Ms) excesses the baseline increase amount (ΔMs), the control device makes the duty ratio be 100% and increases the rotation speed of the engine from the low idling speed correspondingly to the operation amount of the operation means, and when the increase amount (ΔM) of the operation amount of the operation means from the baseline operation amount (Ms) does not exceed the baseline increase amount (ΔMs), the control device maintains the rotation speed of the engine at the low idling speed (Nlow). an engine; an outdrive device having a propeller rotated by power of the engine; a clutch selectively engaging for making a power transmission from the engine to the propeller or disengaging for cutting off the power transmission from the engine to the propeller; an operation means actuating the outdrive device; and a control device connected to the engine, the clutch and the operation means, wherein the control device stores a duty ratio, a baseline operation amount (Ms) of the operation means, and a baseline increase amount (ΔMs) of an operation amount of the operation means, wherein the duty ratio is set as a ratio of a time of engaging the clutch to a predetermined cycle, wherein the control device has a very low speed sailing mode, wherein the control device is connected to a determination means determining whether the very low speed sailing mode is executed or not, and wherein in a case in which execution of the very low speed sailing mode is determined, when the operation amount of the operation means is not more than the baseline operation amount (Ms), the control device makes a rotation speed of the engine be a low idling rotation speed (Nlow) and changes the duty ratio in a range not more than 100%, correspondingly to the operation amount of the operation means, characterized in that when the operation amount of the operation means excesses the baseline operation amount (Ms), and an increase amount (ΔM) of the operation amount from the baseline operation amount (Ms) excesses the baseline increase amount (ΔMs), the control device makes the duty ratio be 100% and increases the rotation speed of the engine from the low idling speed correspondingly to the operation amount of the operation means, and when the increase amount (ΔM) of the operation amount of the operation means from the baseline operation amount (Ms) does not exceed the baseline increase amount (ΔMs), the control device maintains the rotation speed of the engine at the low idling speed (Nlow).