A connection structure embedded substrate includes a printed circuit board including a plurality of first insulating layers, and a plurality of first wiring layers disposed on or between the plurality of first insulating layers; and a connection structure embedded in the printed circuit board, and including a plurality of second insulating layers and a plurality of second wiring layers disposed on or between the plurality of second insulating layers. A lowermost second insulating layer of the plurality of second insulating layers includes an organic insulating material, and is in contact with an upper surface of one of the plurality of first insulating layers.