A method of progressive processing comprising: a feeding step of feeding a strip-shaped sheet to a press machine; a pressing step of pressing the strip-shaped sheet with the press machine; and a joining step of joining the strip-shaped sheet with a new strip-shaped sheet by applying a tape over an end of the strip-shaped sheet located in a direction opposite a direction in which the strip-shaped sheet is fed and an end of the new strip-shaped sheet located in a direction in which the new strip-shaped sheet is fed, a first cutting step of forming a first cut surface inclined with respect to the direction in which the strip-shaped sheet is fed on the strip-shaped sheet by obliquely cutting, with respect to the direction in which the strip-shaped sheet is fed, the end of the strip-shaped sheet located in the direction opposite the direction in which the strip-shaped sheet is fed, and a second cutting step of forming a second cut surface oriented along the first cut surface on the new strip-shaped sheet by cutting the end of the new strip-shaped sheet located in the direction in which the new strip-shaped sheet is fed in a direction oriented along the first cut surface, wherein the joining step applies the tape over the ends of the upper surface of the two strip-shaped sheets so as to be oriented obliquely along the first cut surface and the second cut surface, wherein, after the joining step, the new strip-shaped sheet is fed to the press machine subsequent to the strip-shaped sheet by performing the feeding step, and the new strip-shaped sheet is pressed subsequent to the strip-shaped sheet by performing the pressing step, and wherein the tape employed in the joining step comprises a tape colored differently from the strip-shaped sheet and the new strip-shaped sheet, and wherein the joining step applies the tape over one side of the strip-shaped sheet and one side of the new strip-shaped sheet on the same side as the strip-shaped sheet. a feeding step of feeding a strip-shaped sheet to a press machine; a pressing step of pressing the strip-shaped sheet with the press machine; and a joining step of joining the strip-shaped sheet with a new strip-shaped sheet by applying a tape over an end of the strip-shaped sheet located in a direction opposite a direction in which the strip-shaped sheet is fed and an end of the new strip-shaped sheet located in a direction in which the new strip-shaped sheet is fed, a first cutting step of forming a first cut surface inclined with respect to the direction in which the strip-shaped sheet is fed on the strip-shaped sheet by obliquely cutting, with respect to the direction in which the strip-shaped sheet is fed, the end of the strip-shaped sheet located in the direction opposite the direction in which the strip-shaped sheet is fed, and a second cutting step of forming a second cut surface oriented along the first cut surface on the new strip-shaped sheet by cutting the end of the new strip-shaped sheet located in the direction in which the new strip-shaped sheet is fed in a direction oriented along the first cut surface, wherein the joining step applies the tape over the ends of the upper surface of the two strip-shaped sheets so as to be oriented obliquely along the first cut surface and the second cut surface, wherein, after the joining step, the new strip-shaped sheet is fed to the press machine subsequent to the strip-shaped sheet by performing the feeding step, and the new strip-shaped sheet is pressed subsequent to the strip-shaped sheet by performing the pressing step, and wherein the tape employed in the joining step comprises a tape colored differently from the strip-shaped sheet and the new strip-shaped sheet, and wherein the joining step applies the tape over one side of the strip-shaped sheet and one side of the new strip-shaped sheet on the same side as the strip-shaped sheet.