To provide a number-of-fine-particle and turbidity measuring instrument that can be improved in measurement accuracy by controlling flow rates in a turbidity meter and a fine particle meter using laser light with high accuracy.

The number-of-fine-particle and turbidity measuring instrument finds the number of fine particles contained in a fixed quantity of sample by projecting the laser light 2 upon a detection tube 1 through which the sample flows and the turbidity of the sample based on the found number of fine particles. In the instrument, flowmeters 3 and 4 are respectively arranged on the upstream and downstream sides of a detecting section A which projects the laser light 2 upon the tube 1. In addition, one of the flowmeters 3 and 4 is constituted of an ultrasonic flowmeter.