The invention relates to a chemical production device and aims to provide a device for preparing biodiesel from microalgae biomass by means of ester exchange and then extraction. The device comprises a multifunctional kettle, a solvent storage tank, a solvent condenser, a distillation still, a biodiesel storage tank, a methyl ester condenser, an air balance tank and a vacuum pump. The top of the multifunctional kettle is connected with the solvent condenser which is connected with the solvent storage tank. The solvent storage tank is connected with the air balance tank. The bottom of the multifunctional kettle is connected with the top of the distillation still. The top of the distillation still is connected with the methyl ester condenser which is connected with the biodiesel storage tank. The biodiesel storage tank is connected with the air balance tank which is connected with the vacuum pump. Without using a highly-toxic extraction chloroform agent, microalgae biomass is utilized for preparing the biodiesel efficiently and fast, efficiency is high, cost is low, production operation is safe and easy, and the device has a wide industrial application prospect.