A substrate treatment apparatus, which treats a substrate with a treatment liquid that is ultrasonically vibrated, includes an oscillator body which is rectangular-parallelepiped and has a treatment liquid supply path having an opening on a lower surface thereof in a first end portion in a longitudinal direction thereof and inclining to a second end portion in the longitudinal direction thereof, a vibrator which is provided on an upper surface of the oscillator body and ultrasonically vibrates the oscillator, and a heat exchanger which cools the treatment liquid supplied to the treatment liquid supply path.