There is provided a resin composition which can be thermoset at a temperature of approximately 80° C., and has excellent PCT resistance and a long pot life. This resin composition is suitable as a one-component adhesive agent to be used during the manufacture of image sensor modules or electronic components. The resin composition according to the present invention is a resin composition having the following characteristics. The resin composition includes (A) a compound represented by formula (1) below, an oligomer having as its basic skeleton a structure represented by formula (2) below, (C) an epoxy resin, and (D) a curing accelerator. The mass ratio ((B)/(A)) between the compound of the (A) component and the oligomer of the (B) component is 5 to 25%. Furthermore, the total content of the compound of the (A) component and the oligomer of the (B) component is 0.5 equivalents to 2.5 equivalents in terms of the ratio of the thiol equivalent of the compound of the (A) component and the oligomer of the (B) component with respect to the epoxy equivalent of the (C) component. In addition, the chloride ion concentration in the resin composition is 230 ppm or less.