The disclosure is directed to an air purifier and an automobile air conditioner with an air purifier. The air purifier includes a reactor, a column, an air guider and a plurality of light emitting elements. The reactor includes an air inlet and an air outlet. The column is disposed in the reactor, and the column has a N-side walls. The air guider is disposed on the column, and the air guider is coated with a photocatalyst. The light emitting elements are placed on the N side walls of the column configured to irradiate on the photocatalyst, where each of the light emitting elements has an emitting angle of θ and θ*N>360°.