A particle separating and measuring device includes a first flow path device having a post-separation flow outlet to allow discharge of a first fluid containing target particles to be separated, and a second flow path device receiving the first flow path device and having a first flow inlet to receive the first fluid. The first flow path device having a lower surface having the post-separation flow outlet is on the second flow path device having an upper surface having the first flow inlet in a first region, with the post-separation flow outlet facing and connecting to the first flow inlet. A connection flow path vertically extends from an opening of the first flow inlet to a first flow path, and narrows from the opening of the first flow inlet toward the first flow path.