To provide a manufacturing method of a porous honeycomb structure capable of preventing generation of defects.

A drying device 100 dries the honeycomb structure 11 (workpiece) received in a drying case 110. That is, a control portion 160 calculates a mass reduction rate by dividing the difference between the mass of workpiece before drying and that after drying in the last drying process, by a mass before drying. Then the control portion 160 measures the mass of the workpiece before drying in the present drying process by a detection signal of a mass detecting portion 130. Then the control portion 160 determines the correction amount to a microwave output and an irradiation time (drying condition) on the basis of the mass reduction rate, and corrects the drying conditions with the correction amount. Then the control portion 160 generates the microwave on the basis of the drying conditions after the collection from a microwave transmitter 140. Then the control portion 160 measures the mass of the workpiece after drying in the present drying process by the detection signal of the mass detecting portion 130.