A connection structure-embedded substrate includes: a printed circuit board including a plurality of first insulating layers of which at least one has a cavity provided therein, a plurality of first wiring layers disposed as at least one of an outer portion and an inner portion of the plurality of first insulating layers, and a first build-up insulating layer disposed on an upper surface of the plurality of first insulating layers; and a connection structure at least partially disposed in the cavity. The first build-up insulating layer is disposed in the cavity, and each of a lower surface of the connection structure and a lower surface of the cavity is in contact with at least a portion of the first build-up insulating layer, respectively.