A hollow poppet valve,, comprising; a stem; a valve head integrally formed at one end of the stem; and an internal cavity, (S') that extends from inside the valve head into the stem, the internal cavity, (S') loaded with a coolant together with an inert gas, wherein the internal cavity, (S') has a valve head cavity, (S'1) of a large inner diameter formed in the valve head and a linear stem cavity of a small inner diameter formed in the stem and communicated with a central region of the valve head cavity, (S'1) at a substantially right angle, wherein the stem cavity has a first portion near the valve head and a second portion near a stem end of the stem, both portions configured such that the second portion has a larger inner diameter than the first portion, wherein an annular step is formed in, and at a predetermined axial position of, the stem cavity, and wherein a turbulent flow, of the coolant is created in the stem cavity downstream of the annular step during reciprocating axial motion of the valve,, characterized in that the internal cavity, (S') is loaded with the coolant from the valve head cavity, (S'1) to a level above the annular step in the stem cavity, in that the valve head cavity is configured in the shape of a substantially truncated circular cone having a tapered conic surface in parallel to an outer periphery of the valve head; in that a peripheral region located around an open end of the stem cavity and forming a ceiling (14b1) of the valve head cavity is a planar face substantially perpendicularly to the central axis of the hollow poppet valve, and in that, in response to the reciprocating axial motion of the valve, a vertical inner perimetric circulatory or convective flow (F1, F2, F3), (F6, F8) of the coolant is created in the valve head cavity around the central axis of the valve, while turbulent flows,, of the coolant are created in the stem cavity. a stem; a valve head integrally formed at one end of the stem; and an internal cavity, (S') that extends from inside the valve head into the stem, the internal cavity, (S') loaded with a coolant together with an inert gas, wherein the internal cavity, (S') has a valve head cavity, (S'1) of a large inner diameter formed in the valve head and a linear stem cavity of a small inner diameter formed in the stem and communicated with a central region of the valve head cavity, (S'1) at a substantially right angle, wherein the stem cavity has a first portion near the valve head and a second portion near a stem end of the stem, both portions configured such that the second portion has a larger inner diameter than the first portion, wherein an annular step is formed in, and at a predetermined axial position of, the stem cavity, and wherein a turbulent flow, of the coolant is created in the stem cavity downstream of the annular step during reciprocating axial motion of the valve,, characterized in that the internal cavity, (S') is loaded with the coolant from the valve head cavity, (S'1) to a level above the annular step in the stem cavity, in that the valve head cavity is configured in the shape of a substantially truncated circular cone having a tapered conic surface in parallel to an outer periphery of the valve head; in that a peripheral region located around an open end of the stem cavity and forming a ceiling (14b1) of the valve head cavity is a planar face substantially perpendicularly to the central axis of the hollow poppet valve, and in that, in response to the reciprocating axial motion of the valve, a vertical inner perimetric circulatory or convective flow (F1, F2, F3), (F6, F8) of the coolant is created in the valve head cavity around the central axis of the valve, while turbulent flows,, of the coolant are created in the stem cavity. wherein the internal cavity, (S') has a valve head cavity, (S'1) of a large inner diameter formed in the valve head and a linear stem cavity of a small inner diameter formed in the stem and communicated with a central region of the valve head cavity, (S'1) at a substantially right angle, wherein the stem cavity has a first portion near the valve head and a second portion near a stem end of the stem, both portions configured such that the second portion has a larger inner diameter than the first portion, wherein an annular step is formed in, and at a predetermined axial position of, the stem cavity, and wherein a turbulent flow, of the coolant is created in the stem cavity downstream of the annular step during reciprocating axial motion of the valve,, characterized in that the internal cavity, (S') is loaded with the coolant from the valve head cavity, (S'1) to a level above the annular step in the stem cavity, in that the valve head cavity is configured in the shape of a substantially truncated circular cone having a tapered conic surface in parallel to an outer periphery of the valve head; in that a peripheral region located around an open end of the stem cavity and forming a ceiling (14b1) of the valve head cavity is a planar face substantially perpendicularly to the central axis of the hollow poppet valve, and in that, in response to the reciprocating axial motion of the valve, a vertical inner perimetric circulatory or convective flow (F1, F2, F3), (F6, F8) of the coolant is created in the valve head cavity around the central axis of the valve, while turbulent flows,, of the coolant are created in the stem cavity.