To provide a treatment solution-spraying nozzle of a substrate treatment apparatus capable of supplying a treatment solution to the whole surface area of a substrate in a short time and treating the substrate with the treatment solution.

This treatment solution-spraying nozzle 1 is provided with a nozzle main body 43 comprising a treatment solution storing part 42 and a treatment solution discharging outlet 47, an ultrasonic oscillator 41 for providing ultrasonic wave vibration to the treatment solution in the treatment solution storing part 42, a restriction part 48 having a smaller orifice than the treatment solution discharging outlet 47, and a foam discharging hole 44 formed in the ultrasonic oscillator 41 for discharging foams existing in the treatment solution storing part 42 to the outside of the treatment solution storing part 42. The restriction part 48 and the treatment solution discharging outlet 47 are connected with each other by an inner wall 45 having a shape with gradually expanded cross-section toward the treatment solution discharging outlet 47 from the restriction part 48. The inner wall 45 has a de Laval nozzle-like shape smoothly changing along the stream line of the treatment solution passing the inside.