The invention intends to provide an electronic component mounting structure where the repairability and the impact resistance are combined. In an electronic component mounting structure, a plurality of solder balls disposed in plane between an electronic component and a substrate is melted to bond the electronic component and the substrate and a resin of which tensile elongation after the curing is in the range of 5 to 40% is filled in portions that are gaps between the electronic component and the substrate and correspond to at least four corners of the electronic component to reinforce. Since the reinforcement area is small, the repairability such as the easy removability of the resin and the reusability of the substrate are excellent, the resin itself is allowed to expand to the impact at the drop to play a role of reinforcing the bonding without breaking, and the impact resistance is excellent as well.