A light measurement device for measuring light emitted from a myocardial cell held by a sample case having a holding part for holding a sample including the myocardial cell, comprising: a time varying image acquisition means for acquiring time varying image data of a two-dimensional light image by detecting the two-dimensional light image of the sample case including light emitted from the sample held inside the holding part of the sample case; and an analysis processing means for performing analysis processing on the time varying image data, wherein the analysis processing means further comprises: a luminance-value-data acquisition means for acquiring, from a region corresponding to the holding part included in the time varying image data, luminance value data indicating a temporal variation in a luminance value in each of a plurality of pixels defining a region corresponding to the holding part; a luminance-value extraction means for extracting, at each pixel, a peak value and a bottom value of the luminance value, from the luminance value data; and a pixel specifying means for repeatedly calculating at each pixel, from the temporal variation of the luminance values at each pixel, on the basis of peak and the bottom luminance values at said pixel, respective evaluation values, comparing the respective evaluation values at each pixel to a threshold and identifying target pixels defining image data of the myocardial cell, from amongst the plurality of pixels in the time varying image data, on the basis of the comparisons of the respective calculated evaluation values to the threshold at each pixel repeatedly satisfying the condition defined by the threshold value and outputting the target pixels defining the image data of the myocardial cell. a time varying image acquisition means for acquiring time varying image data of a two-dimensional light image by detecting the two-dimensional light image of the sample case including light emitted from the sample held inside the holding part of the sample case; and an analysis processing means for performing analysis processing on the time varying image data, wherein the analysis processing means further comprises: a luminance-value-data acquisition means for acquiring, from a region corresponding to the holding part included in the time varying image data, luminance value data indicating a temporal variation in a luminance value in each of a plurality of pixels defining a region corresponding to the holding part; a luminance-value extraction means for extracting, at each pixel, a peak value and a bottom value of the luminance value, from the luminance value data; and a pixel specifying means for repeatedly calculating at each pixel, from the temporal variation of the luminance values at each pixel, on the basis of peak and the bottom luminance values at said pixel, respective evaluation values, comparing the respective evaluation values at each pixel to a threshold and identifying target pixels defining image data of the myocardial cell, from amongst the plurality of pixels in the time varying image data, on the basis of the comparisons of the respective calculated evaluation values to the threshold at each pixel repeatedly satisfying the condition defined by the threshold value and outputting the target pixels defining the image data of the myocardial cell. a luminance-value-data acquisition means for acquiring, from a region corresponding to the holding part included in the time varying image data, luminance value data indicating a temporal variation in a luminance value in each of a plurality of pixels defining a region corresponding to the holding part; a luminance-value extraction means for extracting, at each pixel, a peak value and a bottom value of the luminance value, from the luminance value data; and a pixel specifying means for repeatedly calculating at each pixel, from the temporal variation of the luminance values at each pixel, on the basis of peak and the bottom luminance values at said pixel, respective evaluation values, comparing the respective evaluation values at each pixel to a threshold and identifying target pixels defining image data of the myocardial cell, from amongst the plurality of pixels in the time varying image data, on the basis of the comparisons of the respective calculated evaluation values to the threshold at each pixel repeatedly satisfying the condition defined by the threshold value and outputting the target pixels defining the image data of the myocardial cell.