STEERING ANGLE DETECTION DEVICE AND ELECTRIC POWER STEERING DEVICE

To calculate a turning angle with respect to a turning angle when a vehicle is traveling straight with high accuracy. A turning angle detecting device includes: a first storage unit (34) configured to store a turning angle neutral point correction value being a difference between a median of the turning angles at respective limits in right steering and left steering and the turning angle when a vehicle is traveling straight; a second storage unit (34) configured to store an initial position of a movable portion of an actuator of a wheel turning mechanism when the vehicle is traveling straight; a first turning angle calculating unit (32) configured to calculate a first turning angle with respect to the median of the turning angles at the respective limits in the right steering and the left steering on a basis of a detection value of a position of the movable portion of the actuator; and a second turning angle calculating unit (35) configured to calculate a second turning angle when the vehicle is traveling straight on a basis of the detection value of the position of the movable portion of the actuator, the turning angle neutral point correction value, the initial position and the first turning angle.