A flip-chip semiconductor package includes a circuit board having a core layer and at least one buildup layer, a semiconductor device connected to the circuit board through a metal bump, and a cured member that is made of a sealing resin composition and enclosed between the semiconductor device and the circuit board. The coefficient of linear expansion at 25 to 75° C. of the cured member is 15 to 35 ppm/° C., the glass transition temperature of at least one buildup layer is 170° C. or more, and the coefficient of linear expansion of at 25 to 75° C. of the at least one buildup layer in the planar direction is 25 ppm or less. A highly reliable flip-chip semiconductor package, buildup layer material, core layer material, and sealing resin composition can be provided by preventing cracks and inhibiting delamination.