A collecting unit is disposed on an exhaust passage of a semiconductor processing apparatus to collect by-products contained in an exhaust gas. The collecting unit includes a trap body detachably disposed inside a casing and configured to collect a part of the by-products. The trap body includes fins arrayed in a flow direction of the exhaust gas and having a surface on which a part of the by-products is deposited and trapped. The collecting unit further includes a receiving mechanism disposed inside the casing and configured to receive a part of the by-products that peels off from the trap body or an inner surface of the casing to prevent this part from being deposited on a bottom of the casing. The receiving mechanism is configured to allow a part of the by-products held thereon to be in contact with a cleaning gas from above and from below.