The dilute chemical solution supply device (1) comprises: a dilute chemical solution preparation unit (2) that prepares a dilute chemical solution (W1); a reservoir (3) for the prepared dilute chemical solution; a dilute chemical solution adjustment/supply mechanism (4) that supplies, as washing water (W2), the dilute chemical solution (W1) stored in the reservoir (3) to a plurality of single-wafer type washers (5A, 5B, and 5C); and a return mechanism that is connected to each of the single-wafer type washers (5A, 5B, and 5C) and refluxes excess water from the single-wafer type washers to the reservoir (3). According to such a dilute chemical solution supply device, it is possible to accurately adjust the concentration of the solute of the dilute chemical solution and suppress the discharge of excess water, and the dilute chemical solution supply device is thus suitable for washing of wafers, etc.

To realize excellent durability of an apparatus, realize a dissolved gas amount suitable for propagation of ultrasonic waves, and stably generate fine bubbles that further comply with a treatment using ultrasonic waves. An ultrasonic treatment apparatus according to the present invention includes: a treatment part capable of accommodating a treatment liquid and an object to be treated; an ultrasonic generator that is provided in the treatment part and applies ultrasonic waves to the object to be treated; and a circulation path for circulating the treatment liquid in the treatment part, in which a fine bubble generator which performs deaeration on an extracted treatment liquid and generates fine bubbles in the treatment liquid, is provided to the circulation path, in series with a treatment liquid extraction pipe. The fine bubble generator has two or more narrow portions each having an opening flow path with a size narrower than an inside diameter of the treatment liquid extraction pipe, in which the opening flow paths of the narrow portions adjacent to each other are configured to prevent the treatment liquid from proceeding straight, and an opening cross-sectional area at each pressure reduction zone satisfies a predetermined relation.