To provide a technology for improving versatility in a semiconductor device using a USB clock or a system clock or the like.

A plurality of clocks(an input clock 1, an input clock 2) are input, and each of those plurality of clocks is measured in a fixed time by an input clock 1 counter 110a and an input clock 2 counter 110b, and the frequency of each of the plurality of clocks is detected by using the measurement result, and any of the plurality of clocks is selected by a clock source selecting circuit 107b based on the detection result, and multiplied by a PLL circuit 2(108b), and frequency-divided by a frequency-dividing circuit 2(109b), and a USB clock is generated.