The invention relates to an angle calibrating device and belongs to the detection field. The calibrating device for a borehole clinometer is characterized by comprising an angle encoder, a sample clamp and a corner drive mechanism, wherein the angle encoder is used as a main calibrating device, the sample clamp is used for fixedly installing the borehole clinometer to be detected, the angle encoder is horizontally arranged and connected with the sample clamp through a bearing rotating shaft base, the two sides of the bearing rotating shaft base are respectively provided with one bearing, the first bearing of one side of the bearing rotating shaft base is connected with the angle encoder, the second bearing of the other side of the bearing rotating shaft base is connected with the sample clamp, the angle encoder and the sample clamp rotate with the same rotating shaft and the same angle, and the corner drive mechanism is used for driving the angle encoder to rotate. According to the angle calibrating device, a cohesion type synchronous main shaft is adopted for connection, the coaxial precision is greatly improved, the stability and the reliability of the device are improved, value loss of output angle displacement transmitting from the corner drive mechanism to the bearing rotating shaft base is basically avoided, the calibration sensitivity is improved greatly, the configuration cost of the device is lowered, and the cost performance is greatly improved.