An electrical connector includes a casing, and a first and a second circuit boards. The casing has a bottom shell and a cover. The bottom shell has an inner bottom surface and an open top. A first carrying platform and a second carrying platform protruded from the inner bottom surface. The cover has an inner top surface facing the inner bottom surface. A first and a second holder blocks are protruded from the inner top surface. The first circuit board is carried on the first carrying platform and clamped between the first carrying platform and the first holder block. The second circuit board is carried on the second carrying platform, stacked on the first circuit board, and clamped between the second carrying platform and the second holder block. The second circuit board has an opening for the first holder block to pass.