Power steering device of vehicle

In a vehicle including an idle stop device (2) that automatically stops an engine (3) when predetermined stop conditions including a condition that vehicle speed V is larger than 0 and equal to or lower than predetermined speed V1 hold and an electric power steering device (1), an assist current upper limit value Iah equivalent to an upper limit value of an assist amount in the electric power steering device (1) is set to 0 when the vehicle speed V is 0, the assist current upper limit value Iah is set to a first upper limit value Iah1 larger than 0 when the vehicle speed V is higher than the predetermined speed V1, and, when the engine (3) is automatically stopped by the idle stop device (2), the assist current upper limit value Iah is set to a third upper limit value Iah2 between 0 and the first upper limit value Iah1 when the vehicle V is larger than 0 and equal to or lower than the predetermined speed V1.