A solid-state image pickup device comprising: a multilayer wiring board having a first opening portion; a mounting portion in the first opening portion of the multilayer wiring board which protrudes into the first opening portion of the multilayer wiring board along a first surface of the multilayer wiring board, wherein the mounting portion has a mounting face which faces the opposite side of the multilayer wiring board to the first surface of the multilayer wiring board and defines a second opening portion, and wherein a reference potential electrode is formed on the mounting face; a spacer being covered with a conductive film and fixed to the multilayer wiring board in a state of making the conductive film face contact with the reference potential electrode in the first opening portion of the multilayer wiring board; a solid-state image pickup element fixed to the spacer in a state of face contact with the conductive film of the spacer, the solid-state image pickup element arranged in the first opening portion of the multilayer wiring board; and an optical element fixed to the spacer on the opposite side of the spacer to solid-state image pickup element at a position opposing the solid-state image pickup element, the optical element transmitting light into the first opening portion of the multilayer wiring board, wherein the reference potential electrode is fixed to one side of the spacer in a state of face contact with the conductive film covering the spacer, and the solid-state image pickup element is fixed to the other side of the spacer in a state of face contact with the conductive film covering the spacer, characterized in that the spacer has an outer periphery larger than an inner periphery of the second opening portion of the multilayer wiring board and an opening with an inner periphery smaller than the inner periphery of the second opening portion of the multilayer wiring board. a multilayer wiring board having a first opening portion; a mounting portion in the first opening portion of the multilayer wiring board which protrudes into the first opening portion of the multilayer wiring board along a first surface of the multilayer wiring board, wherein the mounting portion has a mounting face which faces the opposite side of the multilayer wiring board to the first surface of the multilayer wiring board and defines a second opening portion, and wherein a reference potential electrode is formed on the mounting face; a spacer being covered with a conductive film and fixed to the multilayer wiring board in a state of making the conductive film face contact with the reference potential electrode in the first opening portion of the multilayer wiring board; a solid-state image pickup element fixed to the spacer in a state of face contact with the conductive film of the spacer, the solid-state image pickup element arranged in the first opening portion of the multilayer wiring board; and an optical element fixed to the spacer on the opposite side of the spacer to solid-state image pickup element at a position opposing the solid-state image pickup element, the optical element transmitting light into the first opening portion of the multilayer wiring board, wherein the reference potential electrode is fixed to one side of the spacer in a state of face contact with the conductive film covering the spacer, and the solid-state image pickup element is fixed to the other side of the spacer in a state of face contact with the conductive film covering the spacer, characterized in that the spacer has an outer periphery larger than an inner periphery of the second opening portion of the multilayer wiring board and an opening with an inner periphery smaller than the inner periphery of the second opening portion of the multilayer wiring board.