A delay setting data generator generates delay setting data based on rate data. A variable delay circuit delays the test pattern data by a delay time determined by the delay setting data with reference to a predefined unit amount of delay. First rate data designates the period of the test pattern data with a precision determined by the unit amount of delay. Second rate data designates the period of the test pattern data with a precision higher than that determined by the unit amount of delay. The delay setting data generator outputs a first value and a second value in a time division manner at a ratio determined by the second rate data, the first and second values being determined by the first rate data.