A printer includes: a head holder supporting a thermal head; a platen holder supporting a platen roller that presses a printing medium toward the thermal head; an engagement member movably supported by one of the platen holder and the platen roller and engageable with and removable from the head holder; and a moving mechanism configured to move the platen holder and the engagement member and configured to move the engagement member from a disengaged position at which the engagement member is separated from and not engaged with the head holder, to an engaged position at which the engagement member is located at and engaged with the head holder, in conjunction with moving the platen holder from a separated position at which the platen roller is separated from the head holder, to a pressing position at which the platen roller presses the printing medium against the thermal head.