An infusion fluid warming bag (latent-heat-type heat accumulator member) 26 is held in close contact with a rear surface of a tube holding plate 20 fitted in a casing body 12 constituting a tube holding device, so as to be disposed in such a position relative to an infusion fluid tube 16 (held between an upper cover 14 and the tube holding plate 20) that enables an infusion fluid to be warmed. The thus disposed infusion fluid warming bag 26 generates a latent heat generated in a phase change from liquid phase to solid phase, whereby the infusion fluid in the infusion fluid tube 16 is warmed by the latent heat. The latent-heat-type heat accumulating material 28 disposed in the infusion fluid warming bag (latent-heat-type heat accumulator member) 26 rapidly generates the latent heat in the phase change from the liquid phase to the solid phase, and the temperature of the generated heat can be rapidly elevated and then held substantially constant for a relatively large length of time, so that it is possible to rapidly warm the infusion fluid passing through the infusion fluid tube 16 even in a circumstance without availability of a power source, and maintain the warmed infusion fluid at a constant temperature from an initial stage of the warming for a relatively large length of time.
