Provided is a water examination device including: a main body; a cup accommodation unit formed inward from a surface of the main body such that a cup containing a fluid is accommodated therein; a wave source for irradiating a wave toward the cup accommodation unit; a detector for detecting a laser speckle generated by multiple scattering of the irradiated wave in the fluid, at every time point set in advance; and a controller for estimating whether foreign substances exist in the fluid in real-time by using the detected laser speckle.