A comparator includes a first constant current source, a first transistor having a drain connected to the first constant current source, a gate connected to a non-inverted input terminal, and a source connected to an inverted input terminal, a second constant current source connected between the inverted input terminal and a second power supply terminal, a second transistor having a source connected to a first power supply terminal, a gate connected to the drain of the first transistor, and a drain connected to an output terminal, and a third constant current source connected between the drain of the second transistor and the second power supply terminal. An oscillation circuit includes comparators in which at least one of the comparators is a comparator described above.