Abstract: An insulator used in an electrical connector has a plate like portion. The plate like portion has upper and lower surfaces perpendicular to a Z-direction and is elongated in an X-direction. In the lower surface, a plurality of grooves are formed and extend in parallel with each other in a Y-direction. The grooves are arranged with intervals in the X-direction so that a plurality of ridges is formed between the respective neighboring grooves in the X-direction. In the upper surface of the plate like portion, material-depressed portions are provided. Each material-depressed portion extends in the Y-direction and has a shape longer in the Y-direction than in the X-direction. Each material-depressed portion is positioned in correspondence with one of the ridges. The insulator is made of anisotropic resin.