A female connector structure includes a plurality of pin insertion holes arranged in a row to correspond to a plurality of columnar connector pins arranged in a male connector section and adapted to receive the respective connector pins individually inserted thereinto. A pair of connector inner walls is formed externally of the pin insertion holes of opposite ends extending in a depth direction of the pin insertion holes. A pair of grooves is formed on an inner surface of the connector inner wall to be gradually shallower as the groove goes from an opening side of the pin insertion hole toward a deepest side thereof.