To investigate the developmental changes of spatial problem solving ability, blindfolded kindergartners, second and third graders of elementary school, and university students, walked with the guidance of the experimenter through a paths having a 45, 90, or 135 degree right or left angle at its middle point. At the end point of each path, each subject walked directly alone toward the direction of the beginning point of the path. The trials were repeated 12 times. The older group revealed less angle error between the direction of movement and the correct direction, though the average direction of each age group concentrated toward the beginning point. The percentage of the longer turning, which is one of the performance measures for spatial problem solving ability, became low and the reaction time which was needed in moving toward the beginning point became long according to age level. The agreement between the developmental stage of spatial thinking argued in Hart and Moore (1973) and the present results, and the working hypothesis for the relation of the spatial problem solving and the reaction time was discussed.