Abstract: An apparatus for measuring particles in liquid in which a laser beam is projected into the liquid containing particles to be measured which are caused to flow into a measurement zone in a measuring cell, and light scattered from the particles passing through the measurement zone is received by the light receiving means to measure characteristics of the particles. The light receiving means is disposed with its optical axis nearly perpendicular to the axis of projection of laser light. The measuring cell has inlet and outlet liquid passages communicating with the measurement zone, the liquid passages having cylindrical portions which communicate through inclined portions with the measurement zone to assure a laminar flow of the liquid through the measurement zone.