Provided is an apparatus and method for measuring a concentration level of particulates in water, by measuring a sound generated upon decomposition of particulates in a water sample which is irradiated by a laser beam. The apparatus comprises a laser beam generator for generating and outputting a laser beam, an output control unit for controlling an output of the laser beam to a constant level by a filter disposed in a laser beam path, a beam splitter for splitting a route of the laser beam output of the output control unit into two routes, a laser beam measurement unit for measuring an output intensity of the laser beam and outputting the measured value as an electrical signal, a condensing lens for condensing the laser beam, a sample cell for storing the water sample and positioned in the laser beam path of the condensed laser beam, a beam stopper for absorbing the condensed laser beam to prevent an external leakage of light, an acoustic sensor coupled with the sample cell for measuring a sound generated from the sample cell, and outputting the measured value as an electrical signal, and a control unit for receiving the signal of the acoustic sensor, calculating the concentration of particulates and outputting a device control signal.