A semiconductor device includes: a printed wiring board; plural semiconductor array elements mounted on the printed wiring board in a row with an adhesive, each of the semiconductor array elements including plural semiconductor elements arranged in a row, the semiconductor array elements including a first semiconductor array element and a second semiconductor array element adjacent to the first semiconductor array element, the first semiconductor array element having a first facing surface, the second semiconductor array element having a second facing surface facing the first facing surface; a first contact prevention member that is made of organic material and disposed to project from the first facing surface; and a second contact prevention member that is made of organic material and disposed to project from the second facing surface. The first and second contact prevention members are disposed to abut each other or face each other with a gap therebetween.