PURPOSE: To securely prevent a printing head from being dried when supply of electric power to a printer is stopped, without sacrificing the printing performance of the printer, by a method wherein an operating power for a drying- preventing device for a printing head is obtained from a moving action of a carriage, and the carriage is moved by an auxiliary power source when supply of electric power is stopped.

CONSTITUTION: When a voltage impressed on output lines of a rectifying circuit 52 disappears due to failure of power supply, Curning-OFF of a power source switch or the like, a power source changing-over circuit 53 immediately changes over from an input side to an auxiliary power source part 57, switchingly connects an output side to a stand-by operating circuit 60 and a motor driver 56, and switchingly connects a gate 55 to the circuit 60 side. A switch 61 provided at a predetermined part on the left side of the carriage 3 and in the exterior of a printing range is closed by being pressed by a projecting piece 62 provided at a lower left end part of the carriage 3, whereby the supply of the auxiliary power source is stopped, a rotatable arm 34 is pivoted clockwise, and head caps 31AW31D are fitted respectively to the printing heads 2AW2D to prevent inks from being dried.