A position measurement system for measuring displacement of an observation station viewed from a reference station by receiving radio waves from satellites by these stations, and performing relative position measurement between the stations, having: a short period displacement measurement section for measuring a short period displacement component in each of the stations through independent position measurement; a relative position computing section for performing relative position measurement between said stations; a long period position computing section for inputting a short period displacement component measured by the short period displacement measurement section, a relative position determined by the relative position computing section and an absolute position from the reference station, and determining the absolute position including a long period displacement component by removing the short period displacement component measured by each of the stations; and a radio communication device installed on each of the stations, for transmitting/receiving data to/from another station.