Welding device and method for manufacturing resin-welded workpiece

A welding device (40) fuses resin parts (20, 30) to an electrode plate (11) as a workpiece. The welding device (40) is provided with: a heating unit (54) that melts the resin parts (20, 30) by heating the resin parts (20, 30); a pressing part (51) that fuses the molten resin part (20, 30) to the electrode plate (11) by pressing the molten resin part (20, 30) toward the electrode plate (11) in a pressing direction (Z) via the sheet (60), the pressing part (51) having a pressing surface (51b) that presses the sheet (60); a pair of support sections (73a, 73b) which are disposed apart from each other in a movement direction (T) intersecting the pressing direction (Z), and which support the sheet (60) such that the sheet (60) covers the pressing surface (51b) from the pressing direction (Z); and a movement mechanism (70) that slides the sheet (60) in the movement direction (T) in a state in which the sheet (60) is supported by the support sections (73a, 73b). 一种熔接装置(40)，使树脂部(20、30)熔接到作为工件的电极板(11)。熔接装置(40)具备：加热部(54