An infusion fluid warming apparatus for warming an infusion fluid to a predetermined temperature prior to supply of the infusion fluid into a living body through an infusion fluid tube. The apparatus includes: (a) a tube holding device detachably holding the infusion tube; and (b) a heat accumulator member generating a latent heat in phase change thereof from liquid phase to solid phase. The heat accumulator member is disposed in the tube holding device, so as to warm the infusion fluid passing through the infusion fluid tube that is held by the tube holding device, by the latent heat generated in the phase change from the liquid phase to the solid phase. Also, disclosed is an infusion fluid warming method.