PROBLEM TO BE SOLVED: To provide a fine particle collecting device allowing efficient continuous operation, the device performing aggregation (concentration) treatment using electrophoresis to collect fine particles in a suspension.SOLUTION: This fine particle collecting device continuously or intermittently continuously performs aggregation treatment on the suspension using electrophoresis to collect the fine particles in the suspension. The fine particle collecting device includes: a rotor 11 that is a rotating electrode 11a; and a treatment tank 13 that is a fixed electrode 13a. The fine particle collecting device includes a particle collecting means 34 scraping and collecting the aggregated fine particles adhered to the rotor 11 while rotating the rotor 11. A start point part of flow-down supply liquid of a raw material liquid supply means 17 to the treatment tank 13 and a start point part of flow-down waste liquid of treated liquid from the treatment tank 13 have a droplet formation shape allowing droplets of raw material liquid and treated liquid to flow down.