PURPOSE: To convert a number-of-rotation signal obtained by a sensor to uniform number-of-rotation data even when transmitters having a different number of transmission elements are utilized.

CONSTITUTION: An evaluation apparatus sends a signal to a signal removing device 3 from an input stage 2 and further sends the same to an output stage 12 processing the signal in matching relation to a purpose. The signal is guided from a pulse converter 4 converting the signal to rectangular signals to a frequency divider 5 and one of the rectangular signals is sent to the input terminal (b) of an AND gate 7 and the other one of them is sent to an operation device 8 and, on the basis of an objective value S possible to preset and a real number Z of transmission elements, individual number-ofrotation signals to be masked are determined from a continuous number-of-rotation signal per one rotation of a shaft and sent to the second input terminal 10 of the AND gate 7 to be outputted to the signal removing device 3 by the output terminal thereof and a desired number-of-rotation signal is masked by the short-circuit of the number- of-rotation signals.