A spinning forming device comprising: a receiving jig supporting a central portion of a plate to be formed; a rotating shaft to which the receiving jig is attached; a processing tool that presses a transform target portion of the plate to transform the plate; and a front-side heater that locally heats the transform target portion by induction heating and is disposed at a same side as the processing tool relative to the plate, characterised in that: the front-side heater includes an electric conducting pipe in which a cooling liquid flows, the electric conducting pipe including a coil portion, the coil portion extending in a circumferential direction of the rotating shaft and having a doubled circular-arc shape facing the plate, a first core covering an inner circular-arc portion of the coil portion from an opposite side of the plate, and a second core covering an outer circular-arc portion of the coil portion from the opposite side of the plate; and at least a part of an inner wall portion of the first core has a shape that tapers toward a tip end of the inner wall portion, the inner wall portion being located at a radially inner side of the inner circular-arc portion, or at least the part of the inner wall portion of the first core is thinner than an outer wall portion of the first core, the outer wall portion being located at a radially outer side of the inner circular-arc portion. a receiving jig supporting a central portion of a plate to be formed; a rotating shaft to which the receiving jig is attached; a processing tool that presses a transform target portion of the plate to transform the plate; and a front-side heater that locally heats the transform target portion by induction heating and is disposed at a same side as the processing tool relative to the plate, characterised in that: the front-side heater includes an electric conducting pipe in which a cooling liquid flows, the electric conducting pipe including a coil portion, the coil portion extending in a circumferential direction of the rotating shaft and having a doubled circular-arc shape facing the plate, a first core covering an inner circular-arc portion of the coil portion from an opposite side of the plate, and a second core covering an outer circular-arc portion of the coil portion from the opposite side of the plate; and at least a part of an inner wall portion of the first core has a shape that tapers toward a tip end of the inner wall portion, the inner wall portion being located at a radially inner side of the inner circular-arc portion, or at least the part of the inner wall portion of the first core is thinner than an outer wall portion of the first core, the outer wall portion being located at a radially outer side of the inner circular-arc portion. the front-side heater includes an electric conducting pipe in which a cooling liquid flows, the electric conducting pipe including a coil portion, the coil portion extending in a circumferential direction of the rotating shaft and having a doubled circular-arc shape facing the plate, a first core covering an inner circular-arc portion of the coil portion from an opposite side of the plate, and a second core covering an outer circular-arc portion of the coil portion from the opposite side of the plate; and an electric conducting pipe in which a cooling liquid flows, the electric conducting pipe including a coil portion, the coil portion extending in a circumferential direction of the rotating shaft and having a doubled circular-arc shape facing the plate, a first core covering an inner circular-arc portion of the coil portion from an opposite side of the plate, and a second core covering an outer circular-arc portion of the coil portion from the opposite side of the plate; and at least a part of an inner wall portion of the first core has a shape that tapers toward a tip end of the inner wall portion, the inner wall portion being located at a radially inner side of the inner circular-arc portion, or at least the part of the inner wall portion of the first core is thinner than an outer wall portion of the first core, the outer wall portion being located at a radially outer side of the inner circular-arc portion.