1. A measurement device comprising: a light source to emit measurement light within a predetermined wavelength band, the light source being arrangeable to emit the measurement light toward a measurement region of a living body; a detection apparatus to detect emitted measurement light, the detection apparatus being arrangeable to detect the emitted measurement light from the living body, the detection apparatus having (i) a micro lens array which includes a plurality of lenses arranged in a predetermined arrangement and which has a light incident side, (ii) a sensor device having one or more respective sensor pixels corresponding to each of a plurality of micro lenses in the micro lens array to measure an intensity of the emitted measurement light thereon, (iii) a first light shield provided on the light incident side of the micro lens array to control directivity of the emitted measurement light onto the light incident side of the micro lens array, and (iv) a second light shield and a diaphragm provided between a side of the micro lens array which is opposite to the light incident side thereof and the sensor device to control directivity of the emitted measurement light after passing through the micro lens array; and a processing device to perform a predetermined process to specify a measurement position from the measurement region for measuring information on pulsation of the living body based respectively on a temporal change in an amount of light of the sensor pixels corresponding to each of a number of the lenses of the micro lens array as detected by the detection apparatus, wherein the processing device during operation calculates a pulse waveform derived from arterial pulsation inside the living body corresponding to the measurement region.