Provided are a dynamic quantity measuring device having higher accuracy and longer-term reliability than in the prior art, and a pressure sensor using the same. A dynamic quantity measuring device is provided with a first Wheatstone bridge configured by an impurity diffused resistor on a principal surface of one semiconductor substrate, and detects a difference between strain quantities respectively generated in an x-axis direction and a y-axis direction that are orthogonal to each other on the principal surface of the semiconductor substrate by the first Wheatstone bridge, the dynamic quantity measuring device being provided with, on the principal surface of the semiconductor substrate, a second Wheatstone bridge for detecting the strain quantity in the x-axis direction, and a third Wheatstone bridge for detecting the strain quantity in the y-axis direction.