The present invention provides a flip chip mounting substrate which comprises an electronic circuit composed of a circuit line and plural mounting pads connected to both ends of the circuit line formed on one surface of a base sheet, wherein the plural mounting pads are faced each other and spaced a pad clearance gap apart, and one or more semiconductor mounting paste guide paths are formed in the mounting pads. The flip chip mounting substrate can reduce voids that might be produced in the semiconductor mounting paste, when flip-chip-mounting an IC chip on a flip chip mounting substrate.