A process for manufacturing a heterojunction solar cell comprising a laminate comprising at least a metal substrate, an n-type single-crystal silicon layer, an n-type transparent semiconductor layer and a transparent protective film, a surface of the transparent protective film serving as a light-receiving surface, and the process comprising the steps of: providing the metal substrate and the n-type single-crystal silicon substrate; implanting at least one of a hydrogen ion and a noble gas ion into the n-type single-crystal silicon substrate so as to form an ion-implanted layer; adhering an ion-implanted surface of the n-type single-crystal silicon substrate to the metal substrate via an electroconductive adhesive; curing the electroconductive adhesive to form an electroconductive adhesion layer so that the n-type single-crystal silicon substrate and the metal substrate can laminate together; giving an impact to the ion-implanted layer to mechanically and partially delaminate the n-type single-crystal silicon substrate so as to leave an n-type single-crystal silicon layer on the metal substrate; depositing an n-type transparent semiconductor layer on the n-type single-crystal silicon layer; forming a collecting electrode on a part of the n-type transparent semiconductor layer; forming a transparent protective film on both the n-type transparent semiconductor layer and the collecting electrode; and, wherein the electroconductive adhesion layer comprises transparent electroconductive material, and comprises light scattering particles having a high refractive index or has microscopic voids having a size of about 0.1 μm or more for light scattering; and wherein a material of the light scattering particles having a high refractive index is selected from the group consisting of a molybdenum oxide, and a hafnium oxide. providing the metal substrate and the n-type single-crystal silicon substrate; implanting at least one of a hydrogen ion and a noble gas ion into the n-type single-crystal silicon substrate so as to form an ion-implanted layer; adhering an ion-implanted surface of the n-type single-crystal silicon substrate to the metal substrate via an electroconductive adhesive; curing the electroconductive adhesive to form an electroconductive adhesion layer so that the n-type single-crystal silicon substrate and the metal substrate can laminate together; giving an impact to the ion-implanted layer to mechanically and partially delaminate the n-type single-crystal silicon substrate so as to leave an n-type single-crystal silicon layer on the metal substrate; depositing an n-type transparent semiconductor layer on the n-type single-crystal silicon layer; forming a collecting electrode on a part of the n-type transparent semiconductor layer; forming a transparent protective film on both the n-type transparent semiconductor layer and the collecting electrode; and, wherein the electroconductive adhesion layer comprises transparent electroconductive material, and comprises light scattering particles having a high refractive index or has microscopic voids having a size of about 0.1 μm or more for light scattering; and wherein a material of the light scattering particles having a high refractive index is selected from the group consisting of a molybdenum oxide, and a hafnium oxide.