With a decimal-fraction address representing a position between two continuous sample values and input from a decimal-fraction address calculation block (5-2) assumed as x, a product-sum block (5-5) calculates the value of x(1-x) as the sum of exclusive logical sums by approximating the value of (1-x) with a value obtained by inverting the values of all the bits representing x. With the use of the thusly obtained value, the waveform sample value (the waveform value) at a waveform position designated by the decimal-fraction address x is calculated, and time-divided DCO outputs are generated by using the calculation result and output to an accumulation block (5-6).