An induction-heating cooker (20, 120, 220, 320, 420, 520) comprising: a main body outer frame (21, 521); a top plate that is disposed above the main body outer frame (21, 521); a heating coil disposed below the top plate adapted to induction-heat and having a coil opening; a ferrite (26, 126) positioned below the induction heating coil without covering the coil opening, a metallic magnetic shield plate (27, 127, 227) on which the ferrite (26, 126) is placed and that has a magnetic shield plate opening (27a, 127a, 227b) which is aligned with the coil opening; an infrared sensor arranged below the magnetic shield plate opening (27a, 127a, 227b) adapted to detect an infrared ray radiated from a cooking container when placed onto the top plate over the heating coil and induction heated by the heating coil and passing through the coil opening, and the magnetic shield plate opening (27a, 127a, 227b); characterized in that an insulation plate (25, 125) is placed between the ferrite (26, 126) and the heating coil, the insulation plate (25, 125) having an insulation plate opening (25a, 125a) which is aligned with the coil opening and the magnetic shield plate opening (27a, 127a, 227b); a casing (30, 130, 430) having at least a bottom part (30b, 430b) located below the infrared sensor, a side wall part (30a, 430a) extended upward from the bottom part (30b, 430b) so as to surround the infrared sensor, and a casing opening (30c, 133a, 331c) through which the infrared ray can pass and made from an electrically conductive material; wherein the casing (30, 130, 430) is located entirely below the magnetic shield plate (27, 127, 227) and a spacer (31, 131, 331) intervening between the lower surface of the magnetic shield plate (27, 127, 227) and the upper end of the casing (30, 130, 430), in contact with the lower surface of the magnetic shield plate (27, 127, 227) and the upper end of the casing (30, 130, 430), having a spacer opening (31c, 131b)below the magnetic shield plate opening (27a, 127a, 227b), and made from a material having electrical insulation. a main body outer frame (21, 521); a top plate that is disposed above the main body outer frame (21, 521); a heating coil disposed below the top plate adapted to induction-heat and having a coil opening; a ferrite (26, 126) positioned below the induction heating coil without covering the coil opening, a metallic magnetic shield plate (27, 127, 227) on which the ferrite (26, 126) is placed and that has a magnetic shield plate opening (27a, 127a, 227b) which is aligned with the coil opening; an infrared sensor arranged below the magnetic shield plate opening (27a, 127a, 227b) adapted to detect an infrared ray radiated from a cooking container when placed onto the top plate over the heating coil and induction heated by the heating coil and passing through the coil opening, and the magnetic shield plate opening (27a, 127a, 227b); an insulation plate (25, 125) is placed between the ferrite (26, 126) and the heating coil, the insulation plate (25, 125) having an insulation plate opening (25a, 125a) which is aligned with the coil opening and the magnetic shield plate opening (27a, 127a, 227b); a casing (30, 130, 430) having at least a bottom part (30b, 430b) located below the infrared sensor, a side wall part (30a, 430a) extended upward from the bottom part (30b, 430b) so as to surround the infrared sensor, and a casing opening (30c, 133a, 331c) through which the infrared ray can pass and made from an electrically conductive material; wherein the casing (30, 130, 430) is located entirely below the magnetic shield plate (27, 127, 227) and a spacer (31, 131, 331) intervening between the lower surface of the magnetic shield plate (27, 127, 227) and the upper end of the casing (30, 130, 430), in contact with the lower surface of the magnetic shield plate (27, 127, 227) and the upper end of the casing (30, 130, 430), having a spacer opening (31c, 131b)below the magnetic shield plate opening (27a, 127a, 227b), and made from a material having electrical insulation.