Provided are a surface-treatment device and a surface-treatment method capable of improving surface-treatment quality when an object undergoes surface-treatment. The surface-treatment device is used to treat the surface of an object at least partially immersed in a liquid, and includes: a jetting part that is disposed so as to face the object and jets a treatment liquid toward the treatment surface of the object; and a jetting part rotation means for causing the jetting part to rotate in a plane parallel to the treatment surface of the object and/or an object rotation means for causing the object to rotate in a plane perpendicular to the jetting direction of the treatment liquid jetted from the jetting part.