A sheet material stacking device and an automatic exposure device for a printing plate, capable of stacking a number of interleaf sheets stably and efficiently. A pair of skewered rollers are provided at the sheet material stacking device used for the automatic exposure device. An interleaf sheet, which is fed from an interleaf sheet transport section, is guided by guide plates and nipped by the rollers. The interleaf sheet, while maintaining a so-called stronger pulling tension, is forcibly fed to an interleaf sheet accommodating section and stacked. Even if the interleaf sheet is thin, the interleaf sheet can behave stably as it is being stacked, and a number of the interleaf sheets can be stacked regularly and effectively.