PURPOSE: To facilitate and ensure positioning of a body to be inspected and a probe and scanning at the time of flaw detection in a liquid bath without moving the probe, by embedding the probe in an array type with an acoustic lens face exposed on the upper side of the bottom of the liquid bath.

CONSTITUTION: The bottom side 6a of a liquid bath 6 for sonic flaw detection is formed to have a vertical double structure with a hollow part 10 held therein, and a probe 2 in an array type is embedded in the hollow part 10 of the bottom 6a with an acoustic lens face exposed on the upper side of the bottom 6a. Besides, a reception circuit being necessary for driving the probe 2 and also a switching circuit for selecting a signal are provided inside, and a connector 11 for connection with a flaw detecting apparatus provided outside the liquid bath is provided in the peripheral wall of the hollow part 10. According to this constitution, it is possible to facilitate and ensure positioning of a body to be inspected and the probe 2 and scanning at the time of flaw detection in the liquid bath without moving the probe 2. In addition, the body to be inspected can be inserted into the liquid bath 6 from above the bath and removed therefrom with ease.