A mesh filter for filtering out foreign matter in fluid, comprising: a discoid gate connection part; an outer cylinder positioned concentrically with a central axis of the gate connection part so as to surround the discoid gate connection part; and a filter unit connecting an entire circumference of an outer peripheral surface of the discoid gate connection part to an entire circumference of an inner peripheral surface of the outer cylinder along a radial direction of the discoid gate connection part; wherein, when a virtual plane orthogonal to a central axis of the discoid gate connection part is assumed to be an X-Y plane, the filter unit is formed along the X-Y plane, the filter unit except a connection portion connecting to the discoid gate connection part and a connection portion connecting to the outer cylinder includes a plurality of longitudinal ribs formed at regular intervals in parallel with each other along the X-Y plane, a plurality of transverse ribs formed at regular intervals in parallel with each other along the X-Y plane, the transverse ribs intersecting with the longitudinal ribs, and a plurality of openings formed between the longitudinal ribs and the transverse ribs, the longitudinal ribs are disposed on one of a front side and a rear side of the filter unit, the transverse ribs are disposed on the other of the front side and the rear side of the filter unit, the openings are formed at intersecting portions of longitudinal grooves between the longitudinal ribs adjacent to each other and transverse grooves between the transverse ribs adjacent to each other, and wherein a rib width of each of the longitudinal ribs is identical to a rib width of each of the transverse ribs and a groove width of each of the longitudinal grooves is identical to a groove width of each of the transverse grooves wherein the mesh filter is produced by injecting molten thermoplastic resin from a gate opened toward a cavity portion shaping the gate connection part of a cavity of a metal mold into the cavity portion to form the discoid gate connection part, the outer cylinder, and the filter unit integrally, make rib widths (L2, L3) of the longitudinal ribs and the transverse ribs constant, and make the shapes of the plurality of openings identical, and J Z wherein a front surface of the discoid gate connection part projects from the front surface of the filter unit by the amount equal to the thickness of the filter unit, and a back surface of the discoid gate connection part projects from the back surface of the filter unit by the amount equal to the thickness of the filter unit. a discoid gate connection part; an outer cylinder positioned concentrically with a central axis of the gate connection part so as to surround the discoid gate connection part; and a filter unit connecting an entire circumference of an outer peripheral surface of the discoid gate connection part to an entire circumference of an inner peripheral surface of the outer cylinder along a radial direction of the discoid gate connection part; wherein, when a virtual plane orthogonal to a central axis of the discoid gate connection part is assumed to be an X-Y plane, the filter unit is formed along the X-Y plane, the filter unit except a connection portion connecting to the discoid gate connection part and a connection portion connecting to the outer cylinder includes a plurality of longitudinal ribs formed at regular intervals in parallel with each other along the X-Y plane, a plurality of transverse ribs formed at regular intervals in parallel with each other along the X-Y plane, the transverse ribs intersecting with the longitudinal ribs, and a plurality of openings formed between the longitudinal ribs and the transverse ribs, the longitudinal ribs are disposed on one of a front side and a rear side of the filter unit, the transverse ribs are disposed on the other of the front side and the rear side of the filter unit, the openings are formed at intersecting portions of longitudinal grooves between the longitudinal ribs adjacent to each other and transverse grooves between the transverse ribs adjacent to each other, and wherein a rib width of each of the longitudinal ribs is identical to a rib width of each of the transverse ribs and a groove width of each of the longitudinal grooves is identical to a groove width of each of the transverse grooves wherein the mesh filter is produced by injecting molten thermoplastic resin from a gate opened toward a cavity portion shaping the gate connection part of a cavity of a metal mold into the cavity portion to form the discoid gate connection part, the outer cylinder, and the filter unit integrally, make rib widths (L2, L3) of the longitudinal ribs and the transverse ribs constant, and make the shapes of the plurality of openings identical, and J Z wherein a front surface of the discoid gate connection part projects from the front surface of the filter unit by the amount equal to the thickness of the filter unit, and a back surface of the discoid gate connection part projects from the back surface of the filter unit by the amount equal to the thickness of the filter unit.