An A-phase pulse (S.sub.A) and a B-phase pulse (S.sub.B) are transmitted from a laser interferometic measuring device to a conversion device (5). When the distance-to-be-measured (l) is increasing, a conversion coefficient (D.sub.R) is added to or subtracted from an initial value in an arithmetic calculator (53) at the rising edge and the trailing edge of the pulses (S.sub.A, S.sub.B). The conversion coefficient has a digital value of M-digits and represents a reference distance .lambda./N, where .lambda. is the wavelength of a laser beam (LB.sub.1, LB.sub.2) employed in the laser measuring machine and M and N are positive integers. A predetermined unit distance in the metric system corresponds to a unit number in the (M+1)-th digit. A distance pulse signal (S.sub.L) is generated in response to a carry signal and a borrow signal from the arithmetic calculator, and is used in expressing a change of the distance in the metric system.