The invention relates to a steam generating device. The steam generating device comprises a shell and an atomizer. A heating cavity is formed in the shell. The shell comprises at least one heat conducting wall, and a thin film water heating layer is arranged on each heat conducting wall. A water inlet, a steam exhaust port and an atomization opening are formed in the shell, and communicate with the heating cavity, and the atomizer is arranged on the shell and corresponds to the atomization opening. The steam generating device is compact in overall structure, small in occupied size, high in heating efficiency and high in steam generating rate.