A robot control apparatus includes a sine wave signal-outputting device, an operating device, a command device for outputting a current value, a substracting device, an electric power amplifying device, and a programmable filter. The outputting device outputs sine wave signals of first and second phases having a phase difference of approximate 90.degree. generated by a position shift of a movable portion of a motor for driving an arm of a robot. The operating device determines the difference between a product of a value corresponding to the first phase signal and a value obtained by first-order differentiating a value corresponding to the second phase signal and a product of a value corresponding to the second phase signal and a value obtained by first-order differentiating the value corresponding to the first phase signal. The subtracting device subtracts the current value from the value outputted from the operating device based on the current value, and outputs a signal corresponding to a result the subtraction. The amplifying device outputs a signal to supply electric power to the motor in response to the signal outputted from the subtracting device. A filter operates as one of a high-pass and a band-pass filters according to the difference outputted from the command device, and is provided between the outputting device and the operating device and operates as a high-pass filter when the arm starts moving and the band-pass filter operates when the arm stops in contact with an object, and outputs a signal to the operating device.