Disclosed is a multi-channel peptide synthesizer, including a gas-bath thermotank, a plurality of reactor tubes, a motor, a rotating rack, a liquid-feeding tube, a feeding device, a vacuum tube and a nitrogen tube. The gas-bath thermotank body provides a desired constant temperature for reaction. The reactor tube provides a place for peptide synthesis and resin washing. The motor and the rotating rack are used to fully mix the reaction and cleaning solutions. Various liquid reagents required are fed to the reactor tube through the liquid-adding tube. Various materials required are prepared in advance in the feeding device and directly fed to the reactor tube. The reaction or washing solution in the reactor tube is pumped to a waste liquid tank through the vacuum tube. Nitrogen is introduced into each reactor tube through the nitrogen tube. This device can be applied in batch-wise peptide synthesis using solid-phase methods.