To provide an air bubble detector capable of certainly detecting air bubbles even when liquid stored in a tube body is the one containing a scatterer.

An air bubble detector which detects air bubbles in liquid stored in a nozzle chip 100 consisting of a translucent material includes: a light emission part 20 which irradiates light with the same wavelength as that of absorption peak wavelength of water toward the nozzle chip 100; a light receiving part 22 which is installed on the opposite side of the light emission part 20 on both sides of the nozzle chip 100, and detects light volume of the light passed through the nozzle chip 100; a Z driving part 14 which relatively moves the nozzle chip 100 in the axis direction; and a control part 16 which controls drive of the Z driving part 14, and determines presence/absence of the air bubbles on the basis of variation of transmitted light volume in accordance with relative movement of the nozzle chip 100 in the axis direction.