An automatic head gap adjustment device for a printer has a plunger that protrudes beyond the print head toward the platen, a linear transducer that detects the amount by which the plunger is depressed, and a motor for widening and narrowing the head gap by moving the print head or platen. A controller drives the motor forward, narrowing the head gap, until the signal output by the transducer changes by a certain amount, then drives the motor in reverse for a fixed amount, widening the head gap, then preferably drives the motor forward again by a smaller fixed amount to take up play in the drive mechanism. This device adjusts the head gap accurately despite changes in ambient conditions.