An organic semiconductor device is provided which includes an organic semiconductor layer and an insulating layer. The insulating layer is made of a cured material formed from a composition containing a resin and a crosslinking agent. The resin contains an organic resin having a hydroxyl group. The crosslinking agent contains a compound having at least two crosslinking groups. At least one of the crosslinking groups is a methylol group or an NH group. The composition contains the crosslinking agent in the range of 15 to 45 percent by weight relative to 100 parts by weight in total of the resin and the crosslinking agent.