A dot-matrix printer with a print head having plural print elements which are disposed in a row and selectively activated to form a dot or dots in a vertical row of a dot matrix pattern representing a character, having a device for adding to a content of a memory the numbers of dots which are formed by the elements; a device for measuring a time lapse; a temperature sensor for sensing a temperature of the print head; a device for substracting a predetermined value based upon the temperature sensed by the temperature sensor at predetermined time intervals; a device for checking whether the content of the memory has exceeded a reference value; and a control device for controlling the print head so as to cool the print head if the content of the memory has exceeded the predetermined value.