To provide an infusion pump capable of inserting an infusion tube to an air bubble sensor without crushing even a part thereof when an opening/closing cover is closed and detecting air bubbles inside the infusion tube no matter whose size among two or more kinds of infusion tubes of different diameters is mounted on the infusion pump.

A guide groove part 350 of an air bubble sensor 51 includes a first guide surface 351 on the side far from a rotary shaft 5A of an opening/closing cover 5 and a second guide surface 352 on the side near the rotary shaft 5A, the first guide surface 351 is a surface parallel to an ultrasonic oscillation element 331, and the second guide surface 352 is a surface inclined to the ultrasonic oscillation element 331. As advancing into the guide groove part 350, an interval between the first guide surface 351 and the second guide surface 352 is formed to be narrow. On the inner side of the opening/closing cover 5, a projection 320 for entering into the guide groove part 350 to hold a part of the infusion tube inside the guide groove part 350 when the opening/closing cover is closed is provided.