PURPOSE: To provide a method for obtaining the positional or distance information of a measuring point inside a pipe easily and accurately.

CONSTITUTION: An image pickup means picks up the image of the inside of a pipe in the axial direction thereof. Positional information of a measuring point PD and the information of the center C of cross-section of pipe including the measuring point PD is then determined on the internal image 10' of the pipe presented on the screen 42 of a TV monitor, for example. Positional information of the measuring point is then acquired based on the positional information determined on the image and a previously derived correlation between the position on the image and the actual position of the measuring point.