This paper presents the applicability of a thermophysical handy tester for quality inspection and diagnostic technique such as in-situ measurement of polymeric resin products. Influence of crystallinity known as a rating factor of quality, or filler-concentration upon thermal conductivity is determined for the case of unsaturated polyester resin-products by using the tester. Consequently, good correlations between the thermal conductivity and the crystallinity or the filler concentration are certificated. The variation or the distribution of thermal conductivity of the products molded under various conditions can be detected nondestructively by the tester. As an example, the thermal conductivity distribution around the forming gate is demonstrated, indicating the density-uniformity of the resin product.