For monitoring vital data in telecare systems, performing noncontact plethysmography measurement is important. We herein propose a precise plethysmography measurement method using multispectral video and investigate optimized process conditions for that measurement. Using independent component analysis of combination signals of RGB videos and 900-nm nIR video yields a better reproduction of plethysmography than other combinations. Concerning region-of-interest selection, using a region of high nIR signal area is favorable for plethysmography estimation. With these optimizing conditions, we attempt obtaining more precise measurements of vital data using multispectral video.