In a detection apparatus (100A), an inlet (10) and an outlet (11) are opened and an air introducing mechanism (50) is driven to introduce air to a case (5), and airborne particles are electrically attracted and held on a collecting jig 12. After introduction, the inlet and outlet are closed, and amount of fluorescence received by a light receiving element (9) resulting from irradiation with light emitted from a light emitting element (6) is measured by a measuring unit (40). Thereafter, the collecting jig is heated by a heater (91) and the amount of fluorescence after heating is measured by the measuring unit. Based on the amount of change in the amount of fluorescence before and after heating, the amount of microorganisms collected by the collecting jig is calculated at the measuring unit.