A particle detecting device includes: a chamber; an injection nozzle provided within the chamber; a discharge nozzle that is disposed within the chamber, opposing the injection nozzle; a detecting mechanism that illuminates a sample fluid that is sprayed from the injection nozzle and detects a particle included in the sample fluid; a pressurizing fluid pipe, connected to the chamber, for supplying a pressurizing fluid for pressurizing an interior of the chamber; and a rectifying member that rectifies the pressurizing fluid so that a flow speed distribution of a fluid between the injection nozzle and the discharge nozzle, rectified in an axial direction, is symmetrical in respect to the axial direction.