To provide a bubble detection method and a device capable of detecting comparatively easily existence of bubbles in a liquid, even in the case of the liquid flowing in a liquid transport pipe having a section shape difficult to be deformed for bubble detection.

In this bubble detection method, an ultrasonic wave is transmitted to the liquid from the side of the liquid transport pipe wherein the liquid flows, and the ultrasonic wave passing through the liquid is received, and the bubbles in the liquid are detected based on the received ultrasonic wave. The method is characterized by executing ultrasonic wave transmission/reception on detection positions to the number of n (n: an integer of two or higher) separated in the flowing direction of the liquid in the liquid transport pipe.