To provide a raw water flow path spacer and a spiral membrane element provided with the same wherein the formation of a concentration polarization layer can be suppressed in a region in the vicinity of a separation membrane in a raw water flow path. A raw water flow path spacer 40 is formed by first thread rows M and second thread rows N overlaying each other and is provided alternatingly with a first mesh structure 52 constituted by connecting first square shaped meshes 52a - 52c constituted by the thread rows M, N in the direction of extension of the second thread rows N and a second mesh structure 61 constituted by connecting in the direction of extension of the second thread rows N such that the space between the second thread rows N is smaller than the space between the second threadrows N constituting the first mesh structure 52.