The pipe insert for generating nano-bubbles of the present invention is an insert inserted into a plumbing pipe in the longitudinal direction, wherein, in order to increase the friction surface of a gas-liquid mixed fluid for generating nano-bubbles in the pipe, the body of the insert is configured such that either or both of dividing walls dividing the fluid path space of the pipe and space dividers protruding into the fluid path space of the pipe are formed continuously in the longitudinal direction of the pipe.