<p>Provided is a thin film forming device (electrospray device (100)) that can improve transferability of an opening pattern in a mask (3). Specifically, this thin-film forming device (electrospray device (100)) is provided with a nozzle (1) that sprays in a state in which a voltage is applied to a solution material, and a mask (3) which is disposed in proximity to a substrate (4) between the nozzle (1) and the substrate (4) and includes an opening part (3a) that has a prescribed opening pattern. The present invention is constituted such that the solution material sprayed by the nozzle (1) is deposited as a thin film on the substrate (4) and such that the nozzle (1) side portion (3b) of the opening part (3a) of the mask (3) has an opening surface area larger than the substrate (4) side portion of the opening part (3a) of the mask (3).</p>
