PURPOSE: Device and method of detecting nanoparticle are provided to measure and count the size and number of nanoparticle using change in the width of an electrical signal depending on the size of the nanoparticle when the nanoparticle passes a variable sensing area. CONSTITUTION: A nanopath(200) supplies a space for enabling fluid including nanoparticle for flow and comprises variable sensing areas(210), which have cross-sectional areas depending on the flow direction of the fluid. A detecting unit is arranged on the nanopath, applies electrical field to the variable sensing areas and measures an electrical signal representing the size of the nanoparticle when the nanoparticel passes the variable sensing areas.
