PURPOSE: To eliminate the problem of reading error of a scale and the personal difference in reading the middle value of the scale by correcting the pulses generated in a rotary encoder by a tape traveling in a pulse length measuring equipment by pulses generated from a photo sensor by the marker of a tape.

CONSTITUTION: The amount of travel of a tape 3A of a steel tape measure is transferred as the number of rotations of rollers 8 and 9, and a rotary encoder 10 is rotated by the gear of the shaft edge of the rotary encoder 10 which us engaged with the gear fixed to the axial edge of the roller 9. Two types of pulses with a phase difference are generated by the rotation of the rotary encoder 10 and the pulses are transferred from a pulse length measuring meter to a computer by a transfer cable 5A. The computer judges the traveling direction of the tape 3A from the phase difference of the pulses, adds and subtracts pulses by a counter, calculates the traveling distance of the tape 3A from a measurement zero point, and then digitally displays the length scale of the tape 3A to be measured.