There are provided an apparatus capable of treating biological particles in a sterile state, and a treatment apparatus. An apparatus for forming a liquid flow including biological particles includes: a chamber member; a sample liquid supply portion; a sheath liquid supply portion; and a vibrating electrode member. The chamber member includes a chamber and a flow cell extending from an interior to an exterior of the chamber. The sample liquid supply portion is configured to supply a sample liquid including the biological particles into the chamber. The sheath liquid supply portion is configured to supply a sheath liquid into the chamber. The vibrating electrode member extends from the interior to the exterior of the chamber, is made of an electrically conductive material, and is configured to be capable of supplying an electric charge to the sheath liquid and the sample liquid in the chamber and propagating an ultrasonic vibration.