A method of manufacturing a concave connector substrate includes: a step of preparing a guide substrate having a guide/holding region that guides a plate-shaped connector to a connection position and a cut portion; a step of arranging and aligning two wiring substrates, each having wiring lines and through hole connection portions that are electrically connected to the wiring lines, with both surfaces of the guide substrate, and applying an adhesive to a predetermined region of the guide substrate to bond the wiring substrates to the guide substrate; a step of bending a portion of the wiring substrate toward the inside of the cut portion of the guide substrate and bringing the wiring lines disposed in the bent portion into pressure contact with the inside of the cut portion; and a step of removing a section inside the cut portion to form the guide/holding region.