PURPOSE: To improve the heat radiation of a serial printer having a wire matrix type printing head by making up a carrier on which the printing head is mounted from a heat conductive part provided with a heat radiator.

CONSTITUTION: A carrier 2 attached with a printing head 1 with screws 3 and moving slidably along a support rail 5 is made of a material of excellent heat conductivity, e.g., aluminium, etc. A large number of heat-radiating fins 21 are also provided to the carrier 2. Heat generated in the printing head 1 during the printing period is transmitted through a contact face 4 to the carrier 2 and then discharged from the fins 21 with good efficiency.