A water examination device (100, 500) comprising: a main body (150, 550); a water accommodation unit (160, 560) formed in the main body; a laser (110, 510) for irradiating light toward the water accommodation unit (160, 560); a detector (120, 520) for detecting a laser speckle at every set time period that is set in advance, the laser speckle being generated due to multiple scattering of the light in the water; a controller for estimating existence of impurities in the water in real-time by using the detected laser speckle; and a calibration unit for controlling the laser (110, 510) or the detector (120, 520) such that an intensity of light irradiated from the laser (110, 510) and measured by the detector (120, 520) is within a certain range set in advance, wherein the detector (120, 520) includes a sensor unit and a shutter formed at one side of the sensor unit to block the light incident in the sensor unit, the calibration unit is arranged to control a shutter speed of the shutter; wherein the water accommodation unit (160, 560) includes: a bottom portion (161, 561) formed in the main body; an opened surface opposite to the bottom portion; and a wall portion (162, 562) formed to have a certain angle with respect to the bottom portion (161, 561), wherein an angle between the bottom portion (161, 561) and the wall portion (162, 562) is not a right angle, and wherein the wall portions (162, 562) facing each other are inclined with respect to the bottom portion (161, 561) toward each other, such that laser light reflected by the wall portion proceeds toward a side opposite to the opened surface to the detector. a main body (150, 550); a water accommodation unit (160, 560) formed in the main body; a laser (110, 510) for irradiating light toward the water accommodation unit (160, 560); a detector (120, 520) for detecting a laser speckle at every set time period that is set in advance, the laser speckle being generated due to multiple scattering of the light in the water; a controller for estimating existence of impurities in the water in real-time by using the detected laser speckle; and a calibration unit for controlling the laser (110, 510) or the detector (120, 520) such that an intensity of light irradiated from the laser (110, 510) and measured by the detector (120, 520) is within a certain range set in advance, wherein the detector (120, 520) includes a sensor unit and a shutter formed at one side of the sensor unit to block the light incident in the sensor unit, the calibration unit is arranged to control a shutter speed of the shutter; wherein the water accommodation unit (160, 560) includes: a bottom portion (161, 561) formed in the main body; an opened surface opposite to the bottom portion; and a wall portion (162, 562) formed to have a certain angle with respect to the bottom portion (161, 561), wherein an angle between the bottom portion (161, 561) and the wall portion (162, 562) is not a right angle, and wherein the wall portions (162, 562) facing each other are inclined with respect to the bottom portion (161, 561) toward each other, such that laser light reflected by the wall portion proceeds toward a side opposite to the opened surface to the detector.