A printed wiring board of a multilayer structure comprising: a plurality of substrates including at least a first substrate and a second substrate, the first substrate being formed with a plurality of pads (15, 17) to be electrically connected to a connector, the second substrate being laminated directly on or indirectly via a substrate other than the first substrate on any one of main surfaces of the first substrate, the second substrate being formed with wirings on any one of main surfaces; and an engageable part formed at a connection end portion to be connected to the connector, the engageable part being to be engaged with an engagement part of the connector; characterized in that one or more reinforcement layers (R1, R2) provided on one or more main surfaces possessed by the plurality of substrates, the one or more reinforcement layers being provided at locations at a frontward side with respect to a location at which the engageable part is provided, with reference to a connecting direction when the printed wiring board is connected to the connector, the plurality of pads (15, 17) formed on the first substrate being disposed within the connection end portion at one main surface side of the first substrate, the plurality of pads formed on the first substrate being arranged to form a front array and a rear array in two rows when viewed in the connecting direction to the connector, the wirings formed on the second substrate including first wirings and second wirings, the first wirings being connected through vias penetrating the one or more substrates to first pads of the front array among the plurality of pads arranged to form the front array and the rear array in two rows, the second wirings being connected through vias penetrating the one or more substrates to second pads of the rear array among the plurality of pads arranged to form the front array and the rear array in two rows, the wirings (9, 11) each having a part formed to have a constant width along an inserting direction to the connector and an expanded-width part expanded to have a wider width than the constant width at a side of the connection end portion in the inserting direction to the connector, the expanded-width part being provided at a location corresponding to each of the pads, the expanded-width parts including first expanded-width parts having approximately same shape as that of the first pads and second expanded-width parts having approximately same shape as that of the second pads. a plurality of substrates including at least a first substrate and a second substrate, the first substrate being formed with a plurality of pads (15, 17) to be electrically connected to a connector, the second substrate being laminated directly on or indirectly via a substrate other than the first substrate on any one of main surfaces of the first substrate, the second substrate being formed with wirings on any one of main surfaces; and an engageable part formed at a connection end portion to be connected to the connector, the engageable part being to be engaged with an engagement part of the connector; characterized in that one or more reinforcement layers (R1, R2) provided on one or more main surfaces possessed by the plurality of substrates, the one or more reinforcement layers being provided at locations at a frontward side with respect to a location at which the engageable part is provided, with reference to a connecting direction when the printed wiring board is connected to the connector, the plurality of pads (15, 17) formed on the first substrate being disposed within the connection end portion at one main surface side of the first substrate, the plurality of pads formed on the first substrate being arranged to form a front array and a rear array in two rows when viewed in the connecting direction to the connector, the wirings formed on the second substrate including first wirings and second wirings, the first wirings being connected through vias penetrating the one or more substrates to first pads of the front array among the plurality of pads arranged to form the front array and the rear array in two rows, the second wirings being connected through vias penetrating the one or more substrates to second pads of the rear array among the plurality of pads arranged to form the front array and the rear array in two rows, the wirings (9, 11) each having a part formed to have a constant width along an inserting direction to the connector and an expanded-width part expanded to have a wider width than the constant width at a side of the connection end portion in the inserting direction to the connector, the expanded-width part being provided at a location corresponding to each of the pads, the expanded-width parts including first expanded-width parts having approximately same shape as that of the first pads and second expanded-width parts having approximately same shape as that of the second pads.