A coating/developing device includes: a first laser unit that irradiates a coating liquid with laser light and acquires a state of the coating liquid based on a change in the laser light; and an irradiation propriety determination mechanism that determines whether the first laser unit irradiates the coating liquid with the laser light based on the coating liquid on a liquid bottle side of a position where the laser light is irradiated from the first laser unit in a flow path. The irradiation propriety determination mechanism includes: a second laser unit that acquires color information of the coating liquid; and a controller. The controller determines whether the color information of the coating liquid is predetermined color information that readily absorbs a wavelength of the light irradiated by the first laser unit and executes determining whether to irradiate the coating liquid with the laser light based on the determination result.