PURPOSE: To inspect an existing pile itself and also inspect whether or not the consolidation of a foundation part which is stuck integratedly with the base edge part of the existing pile is sufficiently constructed quantitatively.

CONSTITUTION: The head part of an existing pile 54 is struck by an striking body 2, and vibration from a pile body caused by striking is detected by the vibration detector 1 of the head part of the existing pile 54, and an electric signal corresponding to the vibration caused by a striking impulse is outputted by the vibration detector 1. The electric signal is memorized in a charge amplifier 3 and transmitted to a personal computer 5 through an A/D converter 4, and if a waveform 6 is displayed during vibration, the periods of time until the respective peaks of the reflection of the existing pile 54 and the reflection of a base bottom part are detected from the peak of the striking impulse can be measured based on the waveform 6. Therefore, the length of the foundation consolidation agent 52 which is integrated with the existing pile 54 itself and the base edge part of the existing pile 54 can be measured, thus it is possible to inspect the quality of piling work quantitatively.