A production method of a circuit board, comprising: a first step of filling a through-hole with a first conductive paste, from one surface of a substrate having the through-hole, the first conductive paste obtained by dispersing conductive particles in a solvent, a second step of forming a first conductive part having a portion inserted in the through-hole, the diameter of the portion being smaller than the through-hole, by heating the first conductive paste, a third step of filling a gap between an inner surface of the through-hole and the first conductive part, with a second conductive paste obtained by dispersing conductive particles in a solvent, from the other surface of the substrate, and a fourth step of forming a second conductive part filling the gap between the inner surface of the through-hole and the first conductive part, by heating the second conductive paste for contracting the second conductive paste along with sintering the conductive particles therein, wherein: the proportion of nanoparticles having a diameter smaller than 1 μm in the conductive particles contained in the first conductive paste, is equal to or more than 40 wt%, in the first step, the first conductive paste is applied to a predetermined region in proximity to the edge of the through-hole, along with filling the through-hole, and the second step of forming the first conductive part causes volume contraction in the first conductive paste by heating, in such a manner that the conductive paste filled in the through-hole separates from the inner surface of the through-hole toward the center thereof, thereby reducing the diameter of the portion inserted in the through-hole, along with forming the gap between the first conductive paste and the inner surface of the through-hole. a first step of filling a through-hole with a first conductive paste, from one surface of a substrate having the through-hole, the first conductive paste obtained by dispersing conductive particles in a solvent, a second step of forming a first conductive part having a portion inserted in the through-hole, the diameter of the portion being smaller than the through-hole, by heating the first conductive paste, a third step of filling a gap between an inner surface of the through-hole and the first conductive part, with a second conductive paste obtained by dispersing conductive particles in a solvent, from the other surface of the substrate, and a fourth step of forming a second conductive part filling the gap between the inner surface of the through-hole and the first conductive part, by heating the second conductive paste for contracting the second conductive paste along with sintering the conductive particles therein, wherein: the proportion of nanoparticles having a diameter smaller than 1 μm in the conductive particles contained in the first conductive paste, is equal to or more than 40 wt%, in the first step, the first conductive paste is applied to a predetermined region in proximity to the edge of the through-hole, along with filling the through-hole, and the second step of forming the first conductive part causes volume contraction in the first conductive paste by heating, in such a manner that the conductive paste filled in the through-hole separates from the inner surface of the through-hole toward the center thereof, thereby reducing the diameter of the portion inserted in the through-hole, along with forming the gap between the first conductive paste and the inner surface of the through-hole. the proportion of nanoparticles having a diameter smaller than 1 μm in the conductive particles contained in the first conductive paste, is equal to or more than 40 wt%, in the first step, the first conductive paste is applied to a predetermined region in proximity to the edge of the through-hole, along with filling the through-hole, and the second step of forming the first conductive part causes volume contraction in the first conductive paste by heating, in such a manner that the conductive paste filled in the through-hole separates from the inner surface of the through-hole toward the center thereof, thereby reducing the diameter of the portion inserted in the through-hole, along with forming the gap between the first conductive paste and the inner surface of the through-hole.