A ship steering method to control a ship steering device so as to keep the hull of the ship sailing obliquely without turning, the ship steering device being of the type comprising: - a pair of left and right engines (3A, 3B); - rotation speed changing actuators (4A, 4B) independently changing engine rotation speeds (NA, NB) of the pair of left and right engines; - a pair of left and right outdrive devices (10A, 10B) respectively connected to the pair of left and right engines and rotating screw propellers (15A, 15B) so as to propel a hull; - forward/reverse switching clutches (16A, 16B) disposed between the engines and the screw propellers; - a pair of left and right steering actuators (17A, 17B) respectively independently rotating the pair of left and right outdrive devices laterally; - an operation means setting a traveling direction of a ship; - an operation amount detection means detecting the operation amount of the operation means; and - a control device controlling the rotation speed changing actuators (4A, 4B), the forward/reverse switching clutches (16A, 16B), and the steering actuators (17A, 17B) so as to travel to a direction set by the operation means; the ship steering device further comprising: - correction control start switch, and - a storage means, the method comprising the following steps: • operate joystick so as to make ship sail obliquely; • twisting joystick to generate a turning moment which balances with the turning moment M generated by the lifting power L; • turning correction control start switch on; • calculating the turning moment MP • detecting elevation angle (a) by an elevation angle sensor; • calculating the propulsion powers TA and TB based on twisting amount of joystick or from the engine rotation speed; • calculating of dynamic pressure 1/2pV2 based on propulsion powers (TA, TB); • calculating of hull speed based on dynamic pressure 1/2pV2; • determining correction value based on formula K = MP/V2/C(a) wherein C(a) is a moment coefficient and a function of a; • displaying correction value; • storing K in storage means. - a pair of left and right engines (3A, 3B); - rotation speed changing actuators (4A, 4B) independently changing engine rotation speeds (NA, NB) of the pair of left and right engines; - a pair of left and right outdrive devices (10A, 10B) respectively connected to the pair of left and right engines and rotating screw propellers (15A, 15B) so as to propel a hull; - forward/reverse switching clutches (16A, 16B) disposed between the engines and the screw propellers; - a pair of left and right steering actuators (17A, 17B) respectively independently rotating the pair of left and right outdrive devices laterally; - an operation means setting a traveling direction of a ship; - an operation amount detection means detecting the operation amount of the operation means; and - a control device controlling the rotation speed changing actuators (4A, 4B), the forward/reverse switching clutches (16A, 16B), and the steering actuators (17A, 17B) so as to travel to a direction set by the operation means; - correction control start switch, and - a storage means, • operate joystick so as to make ship sail obliquely; • twisting joystick to generate a turning moment which balances with the turning moment M generated by the lifting power L; • turning correction control start switch on; • calculating the turning moment MP • detecting elevation angle (a) by an elevation angle sensor; • calculating the propulsion powers TA and TB based on twisting amount of joystick or from the engine rotation speed; • calculating of dynamic pressure 1/2pV2 based on propulsion powers (TA, TB); • calculating of hull speed based on dynamic pressure 1/2pV2; • determining correction value based on formula K = MP/V2/C(a) wherein C(a) is a moment coefficient and a function of a; • displaying correction value; • storing K in storage means.