A thermal detector manufacturing method includes: forming a sacrificial layer on a structure including an insulating layer; forming a support member on the sacrificial layer; forming on the support member a heat-detecting element; forming a first light-absorbing layer so as to cover the heat-detecting element, and planarizing the first light-absorbing layer; forming a contact hole in a portion of the first light-absorbing layer, subsequently forming a thermal transfer member having a connecting portion that connects to the heat-detecting element and a thermal collecting portion having a surface area greater than that of the connecting portion as seen in plan view; forming a second light-absorbing layer on the first light-absorbing layer; and removing the sacrificial layer to form a cavity between the support member and the structure including the insulating layer formed on the surface of the substrate.