The invention relates to an indication device. A storage chamber is formed between a starting part of an indication layer and a substrate layer; and an indication unit is arranged in the storage chamber. The indication unit consists of a flexible porous adsorber and a phase-change indication material absorbed into the flexible porous adsorber. When the indication device is activated, the flexible porous adsorber is extruded only by pressing the starting part; the phase-change indication material is separated from the flexible porous adsorber and enters a microporous interlayer by a liquid-phase channel, thereby indicating a temperature change. The pressure needed for pressing and activation is small and the edge of the indication device is not easy to fracture.