PURPOSE: To form a counting device which realizes the count operation of a desired M notation with a simple constitution, by repeating count operations of an N notation and an N+1 notation periodically.

CONSTITUTION: In case that the count operation of am M notation, for example, 12.5 notation, BCD 1011 (decimal 11) is stored in a memory 4; and first, the output of an FF7 is 0, and the output of the memory is set to a down counter 3 through exclusive OR circuits 61∼63 as it is. When 11 count pulses from an input terminal 2 come, the count value becomes 0000; and the count value of the counter 3 becomes 1111 by the 12th pulse input, and a borrow signal B is outputted, and the output of the FF7 is 1, and outputs of circuit 61∼63 are 001, and 1100 is set to the down counter 3. Therefore, the count value of the counter 3 becomes 0000 when the next 12 count pulses come, and the count value becomes 1111 by the 13th pulse, and the borrow signal output is issued, and the FF is set to 0. A count signal of 12.5 notation is taken out as the whole to a borrow signal output terminal.