The invention provides an angle detecting device, which comprises absolute encoders provided on a rotation member which rotates at a constant speed, a clock signal generating component, a counter circuit, an angle calculating component, and a trigger signal generating component, wherein an angle trigger signal is inputted to the absolute encoders and the counter circuit at a predetermined time interval, the absolute encoders input rotation angles for each angle trigger signal to the angle calculating component, the counter circuit outputs the number of clock counts to the angle calculating component from the moment when a rotation angle measuring trigger signal is inputted by inputting the rotation angle measuring trigger signal for detecting the rotation angle of the rotation member to the counter circuit, and wherein the angle calculating component detects the rotation angle of the rotation member based on the rotation angles from the absolute encoders and on the number of the clock counts.