An X-ray tube comprising: an anode comprising a target surface configured to emit an X-ray in a main emission direction from a first focus formed by collision of an electron beam; and a cathode disposed opposite the target surface of the anode, the cathode comprising a first filament configured to emit the electron beam and a focusing electrode configured to focus the electron beam emitted from the first filament, the focusing electrode including a valley bottom portion located farthest from the first focus, a first inclined plane sloping up from the valley bottom portion in a direction of the anode, a first focusing groove opening in the first inclined plane, and a first storage groove opening in a bottom surface of the first focusing groove and storing the first filament, wherein: when an axis passing through a center of the first focus and parallel to an axis of the X-ray tube is a reference axis, a plane including the reference axis and the main emission direction is a first reference surface, and a first angle (θ1) formed by a first extension line and a second extension line crossing each other on an opposite side to a side to which the X-ray is emitted with respect to the reference axis is θ1, the first extension line being a virtual straight line extending from a boundary between the valley bottom portion and the first inclined plane along the first reference surface, the second extension line being a virtual straight line extending from the target surface along the first reference surface and the target surface, θ1>0°; the first focusing groove has a longitudinal axis; one end portion (21e1) on the first extension line side of the first focusing groove is closer to the first reference surface than the other end portion (21e2) of the first focusing groove; characterised in that: the first storage groove has a longitudinal axis orthogonal to the reference axis and parallel to the first reference surface. an anode comprising a target surface configured to emit an X-ray in a main emission direction from a first focus formed by collision of an electron beam; and a cathode disposed opposite the target surface of the anode, the cathode comprising a first filament configured to emit the electron beam and a focusing electrode configured to focus the electron beam emitted from the first filament, the focusing electrode including a valley bottom portion located farthest from the first focus, a first inclined plane sloping up from the valley bottom portion in a direction of the anode, a first focusing groove opening in the first inclined plane, and a first storage groove opening in a bottom surface of the first focusing groove and storing the first filament, wherein: when an axis passing through a center of the first focus and parallel to an axis of the X-ray tube is a reference axis, a plane including the reference axis and the main emission direction is a first reference surface, and a first angle (θ1) formed by a first extension line and a second extension line crossing each other on an opposite side to a side to which the X-ray is emitted with respect to the reference axis is θ1, the first extension line being a virtual straight line extending from a boundary between the valley bottom portion and the first inclined plane along the first reference surface, the second extension line being a virtual straight line extending from the target surface along the first reference surface and the target surface, θ1>0°; the first focusing groove has a longitudinal axis; one end portion (21e1) on the first extension line side of the first focusing groove is closer to the first reference surface than the other end portion (21e2) of the first focusing groove; characterised in that: the first storage groove has a longitudinal axis orthogonal to the reference axis and parallel to the first reference surface. when an axis passing through a center of the first focus and parallel to an axis of the X-ray tube is a reference axis, a plane including the reference axis and the main emission direction is a first reference surface, and a first angle (θ1) formed by a first extension line and a second extension line crossing each other on an opposite side to a side to which the X-ray is emitted with respect to the reference axis is θ1, the first extension line being a virtual straight line extending from a boundary between the valley bottom portion and the first inclined plane along the first reference surface, the second extension line being a virtual straight line extending from the target surface along the first reference surface and the target surface, θ1>0°; the first focusing groove has a longitudinal axis; one end portion (21e1) on the first extension line side of the first focusing groove is closer to the first reference surface than the other end portion (21e2) of the first focusing groove; characterised in that: the first storage groove has a longitudinal axis orthogonal to the reference axis and parallel to the first reference surface.