A limiter circuit compares a voltage of a control gate line and a set voltage, thereby switching the logic of a flag signal. A booster circuit starts or stops its operation according to the logic of the flag signal. A leak reference circuit has a function of leaking a leak reference current from the control gate line. A counter generates a first count value by counting the number of times the flag signal logic changes in a condition that a word-line transfer transistor is rendered non-conductive and a leak reference circuit is driven, while the counter generates a second count value by counting the number of times the flag signal logic changes in a condition that the word-line transfer transistor is rendered conductive and the leak reference circuit is undriven. A comparator compares the first count value and the second count value.