Provided is an elastic seal member and a connector which can suppress deterioration of a sealing property while suppressing an insertion resistance to a wire insertion hole. A plurality of seal insertion holes (electric wire insertion holes) through which terminal-equipped electric wires are inserted in the thickness direction is arranged and provided, and on at least one of the front and back surfaces a thinned groove is provided adjacent to the seal insertion hole (electric wire insertion hole), and the thinned groove is formed into a shape that does not overlap with a circular range centered on the seal insertion hole (electric wire insertion hole) in a plan view when viewing the one surface, the circular range of the electric wire insertion holes (electric wire insertion hole) adjacent to each other interposing the thinned groove being not overlapping with each other.