To provide a pipe interior inspection device having an accurate distance measuring instrument strong against vibration.

Rollers 10 are supported in a freely rotatable manner by the shafts 11 inserted in the leading ends of supports 9 through spacers 12 and bearings 13 and have contact parts 10a having a large outer diameter and magnetizing parts 10b having a small outer diameter. Each contact part 10a comes into contact with the inner wall of a pipeline 1 and each magnetizing part 10b is magnetized so that the outer periphery thereof is alternately set to N- and S-poles. A magnetic sensor 14 is arranged to the leading end of each support 9 and the magnetic field generated from the magnetizing part 10b is detected at the leading end part thereof. When the roller 10 is rotated, the direction of the magnetic field detected by the magnetic sensor 14 is alternately changed and, therefore, sinusoidal output synchronous to the rotation of the roller 10 is generated from the magnetic sensor 14. A distance measuring instrument 8 pulsates this output to count pulses to measure a distance.