By bringing one surface of a band-shaped sheet stack (10) (continuous diaper), in which multiple sheets are stacked, into contact with a support member (21) that has light-passing sections (27) through which laser light (30) can pass and irradiating laser light (30) of a wavelength, which is absorbed by the sheets configuring the sheet stack (10) and causes said sheets to generate heat, on the pressed band-shaped sheet stack (10) through the light-passing sections (27) from the support member (21) side, the band-shaped sheet stack (10) is divided into parts while the cut edges of the pressed multiple sheets generated by said division are simultaneously fused to form a sealed edge (4) (side seal) in which the edges of the multiple sheets are fused in a stacked state.本發明之片材熔合體之製造方法中，使重疊有複數塊片材之帶狀之片材積層體(10)(尿布連續體)之一面抵接於包含可使雷射光(30)通過之光通過部(27)之支持構件(21)，對成為加壓狀態之帶狀之片材積層體(10)，自支持構件(21)側經由光通過部(27)照射由構成該片材積層體(10)之片材吸收且使該片材發熱之波長之雷射光(30)，藉此，將帶狀之片材積層體(10)分斷，與此同時，使藉由上述分斷而產生之處於上述加壓狀態之複數塊片材之切斷緣部彼此熔合，而形成複數塊片材之緣部以重疊之狀態熔合的密封緣部(4)(側封部)。
