A method of processing a product using fabric of the present invention comprises a marking treatment step to mark a position of connection with a trim cloth on a three-dimensional net member (a solid knitted fabric) 11 before uniting the solid knitted fabric which is one fabric and a trim cloth which is the other fabric. Accordingly, a cutting step of a fabric material can be facilitated so that cost of the cutting step can be reduced. Further, occurrence of a remnant at the time of cutting the fabric material can be reduced to almost zero, thereby the availability of the fabric material can be improved.