Nitrocellulose (NC), which is a nitrate ester compound having ONO₂ group in their chemical structure, is an industrially useful material utilized as a raw material for explosives, lacquers, and celluloid products. However, NC is an unstable material that has a risk of undergoing spontaneous decomposition even at low temperatures. Accumulation of decomposition heat can cause spontaneous ignition, and numerous relevant accidental explosions have been reported. Although the NC spontaneous decomposition has already been investigated for a long time, recent accidental explosions like the catastrophe in China in 2015 have made the relevant studies again draw attention from the viewpoint of the safety aspect. The author's research group has comprehensively investigated the spontaneous decomposition behavior of NC so far, using heat flow calorimetry. In this article, the author introduced a part of our achievement and the future tasks related to the thermal decomposition mechanism, hazard evaluation method, and novel stabilizer of NC.