An ultrasonic measurement method comprising: a measuring point setting step of setting an arbitrary measuring point near a weld portion inside of steel material and assuming a virtual reflecting surface that includes the measuring point and is parallel to a weld line direction; a focused beam setting step of transmitting ultrasonic waves of a shear wave mode satisfying Expression 1 and focusing onto the measuring point via a coupling medium at a predetermined incident angle with respect to the virtual reflecting surface; a detecting step of detecting reflected waves of the transmitted ultrasonic waves at a boundary between a base metal portion and the weld portion; and an evaluating step of evaluating a shape of the weld portion based on the reflected waves: V T V R ⋅ F D ≤ 0.30 sinθ Hlim wherein a plurality of virtual reflecting surfaces of different angles are assumed for each measuring point set at the measuring point setting step, where V T (mm/s) is sound velocity of the coupling medium, V R (mm/s) is sound velocity of shear waves at the base metal portion of the steel material as a test subject, D (mm) is a transmitting unit width in a direction orthogonal to the weld line direction, F (mm) is a focal length in coupling medium conversion, and θ Hlim (degrees) is a deviation angle upper limit between the assumed reflecting surface and an actual reflecting surface. a measuring point setting step of setting an arbitrary measuring point near a weld portion inside of steel material and assuming a virtual reflecting surface that includes the measuring point and is parallel to a weld line direction; a focused beam setting step of transmitting ultrasonic waves of a shear wave mode satisfying Expression 1 and focusing onto the measuring point via a coupling medium at a predetermined incident angle with respect to the virtual reflecting surface; a detecting step of detecting reflected waves of the transmitted ultrasonic waves at a boundary between a base metal portion and the weld portion; and an evaluating step of evaluating a shape of the weld portion based on the reflected waves: V T V R ⋅ F D ≤ 0.30 sinθ Hlim wherein a plurality of virtual reflecting surfaces of different angles are assumed for each measuring point set at the measuring point setting step, where V T (mm/s) is sound velocity of the coupling medium, V R (mm/s) is sound velocity of shear waves at the base metal portion of the steel material as a test subject, D (mm) is a transmitting unit width in a direction orthogonal to the weld line direction, F (mm) is a focal length in coupling medium conversion, and θ Hlim (degrees) is a deviation angle upper limit between the assumed reflecting surface and an actual reflecting surface. wherein a plurality of virtual reflecting surfaces of different angles are assumed for each measuring point set at the measuring point setting step, where V T (mm/s) is sound velocity of the coupling medium, V R (mm/s) is sound velocity of shear waves at the base metal portion of the steel material as a test subject, D (mm) is a transmitting unit width in a direction orthogonal to the weld line direction, F (mm) is a focal length in coupling medium conversion, and θ Hlim (degrees) is a deviation angle upper limit between the assumed reflecting surface and an actual reflecting surface.