The invention relates to a device for adjusting a device temperature in a plasma etching cavity and a temperature adjustment method. The temperature adjustment device is arranged in the plasma etching cavity and comprises an insulation sealing assembly, wherein the insulation sealing assembly is arranged in an insulation ring and is connected with a gas supply unit through a gas passage, a plurality of channel spaces are arranged in the insulation sealing assembly and communicate with the gas supply unit through the gas passage, the insulation sealing assembly, the gas passage and the gas supply unit form a closed space, the gas supply unit is used for adjusting gas pressures in the channel spaces by releasing or recycling inert gas so that the thermal conductivity of the insulation sealing assembly is adjusted, and the temperature of a focusing ring is controlled to be higher than the temperature of a substrate by 50-100 DEG C. By the temperature adjustment device, and the temperature adjustment device is simpler and more effective in temperature adjustment of a device in the plasma etching cavity, better in heat conduction effect and is also lower in cost.