A magnetic field measuring device that detects the strength of a magnetic field produced from a magnetic field-producing body, comprising: first to fourth magnetoelectric transducers (11, 12); magnetic convergence plates made up of a magnetic body; and a calculation unit that is configured to calculate the strength of a magnetic field applied in a horizontal direction and/or a vertical direction with respect to a magneto-sensing surface of the magnetoelectric transducers; wherein the magnetic convergence plates are placed in the vicinity of the first to fourth magnetoelectric transducers so as to convert magnetic field vectors produced in a horizontal direction with respect to the magneto-sensing surface of the first magnetoelectric transducer and the magneto-sensing surface of the second magnetoelectric transducer into magnetic field vectors in a vertical direction with respect to the magneto-sensing surface of the first magnetoelectric transducer and the magneto-sensing surface of the second magnetoelectric transducer, such that, in a spatially uniform horizontal magnetic field, a magnetic field is applied to the first magnetoelectric transducer in the negative vertical direction and to the second magnetoelectric transducer in the positive vertical direction, and further, convert magnetic field vectors produced in a horizontal direction with respect to the magneto-sensing surface of the third magnetoelectric transducer and the magneto-sensing surface of the fourth magnetoelectric transducer into magnetic field vectors in a vertical direction with respect to the magneto-sensing surface of the third magnetoelectric transducer and the magneto-sensing surface of the fourth magnetoelectric transducer, such that, in a spatially uniform horizontal magnetic field, a magnetic field is applied to the third magnetoelectric transducer in the negative vertical direction and to the fourth magnetoelectric transducer in the positive vertical direction, and wherein the calculation unit includes a first calculation block that is configured to use each of the outputs from the first to fourth magnetoelectric transducers in adding and subtracting calculations to output a calculation result, and the calculation unit includes a second calculation block that is configured to use each of the outputs from the first to fourth magnetoelectric transducers in adding and subtracting calculations to calculate a signal whose phase differs from an output signal of the first calculation block, and the first to fourth magnetoelectric transducers are placed approximately linearly along the magnetized direction of the magnetic field-producing body. first to fourth magnetoelectric transducers (11, 12); magnetic convergence plates made up of a magnetic body; and a calculation unit that is configured to calculate the strength of a magnetic field applied in a horizontal direction and/or a vertical direction with respect to a magneto-sensing surface of the magnetoelectric transducers; wherein the magnetic convergence plates are placed in the vicinity of the first to fourth magnetoelectric transducers so as to convert magnetic field vectors produced in a horizontal direction with respect to the magneto-sensing surface of the first magnetoelectric transducer and the magneto-sensing surface of the second magnetoelectric transducer into magnetic field vectors in a vertical direction with respect to the magneto-sensing surface of the first magnetoelectric transducer and the magneto-sensing surface of the second magnetoelectric transducer, such that, in a spatially uniform horizontal magnetic field, a magnetic field is applied to the first magnetoelectric transducer in the negative vertical direction and to the second magnetoelectric transducer in the positive vertical direction, and further, convert magnetic field vectors produced in a horizontal direction with respect to the magneto-sensing surface of the third magnetoelectric transducer and the magneto-sensing surface of the fourth magnetoelectric transducer into magnetic field vectors in a vertical direction with respect to the magneto-sensing surface of the third magnetoelectric transducer and the magneto-sensing surface of the fourth magnetoelectric transducer, such that, in a spatially uniform horizontal magnetic field, a magnetic field is applied to the third magnetoelectric transducer in the negative vertical direction and to the fourth magnetoelectric transducer in the positive vertical direction, and wherein the calculation unit includes a first calculation block that is configured to use each of the outputs from the first to fourth magnetoelectric transducers in adding and subtracting calculations to output a calculation result, and the calculation unit includes a second calculation block that is configured to use each of the outputs from the first to fourth magnetoelectric transducers in adding and subtracting calculations to calculate a signal whose phase differs from an output signal of the first calculation block, and the first to fourth magnetoelectric transducers are placed approximately linearly along the magnetized direction of the magnetic field-producing body.