A portable medical liquid infusion device receives an input of a medical liquid infusion rate (cc/hour), the quantity of medical liquid to be infused or the length of time for infusion, and outputs a recognition signal corresponding to the input, thereby allowing a drip interval to be easily adjusted, and which quantitatively calculates and outputs a medical liquid infusion rate on the basis of a count input which is received in accordance with a drip interval when measuring the medical liquid infusion rate. The medical liquid infusion device judges a count input having an irregular interval as an erroneous input, and renders another count input to be conducted again through automatic resetting, whereby the medical liquid infusion device can output a correct measurement result only, and also can output the length of time for infusing the remaining medical liquid when measuring the medical liquid infusion rate.
