Children with congenital forearm deficiency have difficulty in daily activities and body balance problem. Since most electric prostheses have been developed for adult amputees, it is necessary to develop a compact and lightweight electric prosthesis for children to manipulate various daily objects. In this paper, we report a compact and lightweight transradial electric prosthesis for children with forearm deficiency. Based on an electric prosthesis termed as Finch for adult amputees, we designed a smaller electric prosthesis by using a compact actuator and a control unit. We downsized the fingers of the Finch without impairing the workability. The total weight of the developed prosthesis was 274 g, which was about 100 g lighter than that of the conventional electric prosthesis for children. The result of upper limb function evaluation using developed prosthesis participated in a child with congenital forearm deficiency demonstrated that the effectiveness of the prosthesis to manipulate daily objects.