[Problem] To provide a purification device for water to be processed, which may purify the water to be processed with a simple and compact configuration.
[Solution] The purification device for the water to be processed includes a collection pump and a filtration device located downstream of the collection pump. The filtration device includes an inflow port into which the water to be processed having passed through the collection pump flows, a filter that filters the water to be processed, and a discharge port through which filtrate water having passed through the filter is discharged. The inflow port is located above the collection pump. The discharge port is located below the inflow port.