PURPOSE: To reduce the wear and flows of a medium and a head by detecting the exhaustion of a lubricant and the deterioration in lubrication effect between the medium and head by a detection part, outputting the result to a lubricant supplement part according to the difference from some set reference value, and supplementing the lubricant with the output signal.

CONSTITUTION: If the lubricant between the recording medium 1 and head 2 runs dry of if the lubrication effect deteriorates after the recording medium 1 runs for a long time, the current of a motor for disk driving varies. The variation of the motor current is detected by using the detection part 5 for the current for the disk driving, and its output is inputted to a lubricant supplementing mechanism through an amplifier 6. Then, a current flows to a driving electromagnetic coil 8 and an arm 13 rotates to bring a lubricant supplement opening 10 into contact with the medium, supplementing the lubricant. A zero-point adjustment is made previously so as to make the output of the motor current detection part zero when the motor current is smaller than some reference current. Therefore, the lubrication effect is recovered by supplementing a specific amount of lubricant, and the motor current decreases to a normal value to stop the supplementation.