To provide a laser type thickness measurement system that removes an influence of a measurement error due to variation in distance between support points of a laser range finder with temperature, does not require special safety management, and can perform continuous measurement, and a calibration method therefor.

Laser type thickness measurement devices 1 and 2 are set at a predetermined interval Ld, and an operation mode setting unit sets "measurement" to a first laser type thickness measurement device and commands the other second laser type thickness measurement device located downstream in a movement direction to start "thickness correction" processing while the first laser type thickness measurement device executes thickness calibration processing with a thickness reference plate and the second laser type thickness measurement device executes measurement processing. A first thickness measurement value is delayed up to a position corresponding to the interval in the movement direction, the difference between the first thickness measurement value and a second thickness measurement value of the second laser type thickness measurement device is found as a correction value, and a thickness correction is made without interrupting the measurement by the second laser type thickness measurement device.