The application provides an air purifier comprising a shell assembly having air inlets and air outlets, and a filter assembly, an air inflow guide assembly, a fan and a diffusion air outflow assembly sequentially arranged from back to front. The filter assembly can purify air entering the filter assembly via the air inlets and flowing through the filter assembly. The air inflow guide assembly defines a guide channel between the filter assembly and the fan. The fan generates an air flow that flows into a first receiving cavity via the air inlets and sequentially flows through each assembly. The diffusion air outflow assembly can rotate to guide the air flow to the air outlets, enable the air flow to diffuse outwards and decrease the flow velocity of the air flow. The air purifier expands the purification range of the air purifier and improves the purification effect of the air purifier.