An electronic component mounting package includes a first base including an upper surface and a first through-hole vertically formed; a second base having a second through-hole arranged to be overlapped with the first through-hole in a plan view; a sealing material filling the second through-hole; and a signal terminal that is fixed to the second base to pass through the sealing material and has an upper end portion that protrudes upwardly from the upper surface of the first base. The first base includes a plurality of first metal members and a second metal member, and the second metal member is vertically interposed between the plurality of first metal members. A thermal expansion coefficient of the first metal members is larger than a thermal expansion coefficient of the second base. A thermal conductivity of the second metal member is higher than a thermal conductivity of the first metal members.