A method of manufacturing a semiconductor device includes: preparing a semiconductor element having a first metal layer made of first metal on a surface thereof, and a metal substrate made of second metal, the metal substrate having a fourth metal layer made of fourth metal on a surface thereof, and mounting the semiconductor element on the surface thereof; providing metal nanopaste between the first metal layer and the fourth metal layer, the metal nanopaste being formed by dispersing fine particles made of third metal with a mean diameter of 100 nm or less into an organic solvent; and heating, or heating and pressurizing the semiconductor element and the metal substrate between which the metal nanopaste is provided, thereby removing the solvent. Further, each of the first, third and fourth metals is made of any metal of gold, silver, platinum, copper, nickel, chromium, iron, lead, and cobalt, an alloy containing at least one of the metals, or a mixture of the metals or the alloys. By the manufacturing method, it is possible to bond the semiconductor element to the metal substrate favorably.