A plate heat exchanger comprising: a plurality of heat transfer plates stacked to each other; and a gasket interposed between each adjacent heat transfer plates, wherein each of the plurality of heat transfer plates has a front side and a back side, at least one of which has a recessed strip; wherein at least one of the front side and the back side of each of the plurality of heat transfer plates has a gasket fitting groove for fittingly receiving the gasket, the gasket fitting groove intersecting with the recessed strip; and wherein a first flow channel for circulation of a first fluid medium and a second flow channel for circulation of a second fluid medium are alternately formed with each of the plurality of heat transfer plates therebetween, and at least one of the first flow channel and the second flow channel is defined by the gasket interposed between each adjacent heat transfer plates, characterized in that the plate heat exchanger further comprising: a regulating member having a support part that can at least partially support the gasket; wherein each of the plurality of heat transfer plates has a fitting recessed portion for fittingly receiving the regulating member, the fitting recessed portion being formed in recessed manner on the side on which the gasket fitting groove is formed, the fitting recessed portion crossing the recessed strip while extending along the gasket fitting groove; and wherein the support part is arranged along the gasket fitting groove when the regulating member is held in fitting engagement with the fitting recessed portion. a plurality of heat transfer plates stacked to each other; and a gasket interposed between each adjacent heat transfer plates, wherein each of the plurality of heat transfer plates has a front side and a back side, at least one of which has a recessed strip; wherein at least one of the front side and the back side of each of the plurality of heat transfer plates has a gasket fitting groove for fittingly receiving the gasket, the gasket fitting groove intersecting with the recessed strip; and wherein a first flow channel for circulation of a first fluid medium and a second flow channel for circulation of a second fluid medium are alternately formed with each of the plurality of heat transfer plates therebetween, and at least one of the first flow channel and the second flow channel is defined by the gasket interposed between each adjacent heat transfer plates, characterized in that the plate heat exchanger further comprising: a regulating member having a support part that can at least partially support the gasket; wherein each of the plurality of heat transfer plates has a fitting recessed portion for fittingly receiving the regulating member, the fitting recessed portion being formed in recessed manner on the side on which the gasket fitting groove is formed, the fitting recessed portion crossing the recessed strip while extending along the gasket fitting groove; and wherein the support part is arranged along the gasket fitting groove when the regulating member is held in fitting engagement with the fitting recessed portion. a regulating member having a support part that can at least partially support the gasket; wherein each of the plurality of heat transfer plates has a fitting recessed portion for fittingly receiving the regulating member, the fitting recessed portion being formed in recessed manner on the side on which the gasket fitting groove is formed, the fitting recessed portion crossing the recessed strip while extending along the gasket fitting groove; and wherein the support part is arranged along the gasket fitting groove when the regulating member is held in fitting engagement with the fitting recessed portion.