A piezoelectric sensor comprising a linear piezoelectric element that consists of two or more linear piezoelectric elements disposed near a measured object, generating an electrical signal in response to stress applied to the linear piezoelectric element, a signal detector that detects an electrical signal generated by each linear piezoelectric element, an overrun assessing unit that assesses whether or not the size of the electrical signal detected by the signal detector has overrun a predetermined threshold value, for each linear piezoelectric element, a timing recorder that records the timing of overrun of the linear piezoelectric element when the size of the electrical signal has been assessed by the overrun assessing unit to have overrun a predetermined threshold value, and a region identifying unit that identifies the region on the measured object where stress has been applied, based on the timing of overrun of the linear piezoelectric element recorded at the timing recorder, wherein the region identifying unit comprises, a boundary defining unit which, based on the order of overrun of the linear piezoelectric elements recorded at the timing recorder, defines as boundary line the collection of points equidistant from the linear piezoelectric element that has been assessed to have overrun, and the next linear piezoelectric element that has been assessed to have overrun following overrun of that linear piezoelectric element, and a region establishing unit which establishes, as the region of stress application, the region that has the boundary line defined by the boundary defining unit and includes the linear piezoelectric element that was initially assessed to have overrun. a linear piezoelectric element that consists of two or more linear piezoelectric elements disposed near a measured object, generating an electrical signal in response to stress applied to the linear piezoelectric element, a signal detector that detects an electrical signal generated by each linear piezoelectric element, an overrun assessing unit that assesses whether or not the size of the electrical signal detected by the signal detector has overrun a predetermined threshold value, for each linear piezoelectric element, a timing recorder that records the timing of overrun of the linear piezoelectric element when the size of the electrical signal has been assessed by the overrun assessing unit to have overrun a predetermined threshold value, and a region identifying unit that identifies the region on the measured object where stress has been applied, based on the timing of overrun of the linear piezoelectric element recorded at the timing recorder, wherein the region identifying unit comprises, a boundary defining unit which, based on the order of overrun of the linear piezoelectric elements recorded at the timing recorder, defines as boundary line the collection of points equidistant from the linear piezoelectric element that has been assessed to have overrun, and the next linear piezoelectric element that has been assessed to have overrun following overrun of that linear piezoelectric element, and a region establishing unit which establishes, as the region of stress application, the region that has the boundary line defined by the boundary defining unit and includes the linear piezoelectric element that was initially assessed to have overrun.