Dynamic images of positron distribution in artery was measured from the skin surface of human subject using beta camera for noninvasive measurement of the input function. After estimating the possibility of the method by some phantom studies, the beta camera was attached from the skin surface on the artery of wrist during the PET measurement using the O-15 water injection method. After injection of O-15 water, dynamic images of the artery were measured. Regions of interest(ROIs) were set on the artery and on the adjacent area of the artery. From the ROIs analysis, a time activity curve similar to input function was noninvasively obtained.