The observation of the crustal deformation has contributed to the researches and studies in seismology and geodesy. Recent advance of space geodetic techniques including GPS (Global Positioning System) and InSAR (Synthetic Aperture Radar Interferometry) greatly improved the accuracy and spatio-temporal resolution to observe the crustal deformation on land. Networks of borehole tiltmeters and strainmeters enabled us to detect very small signals related with slow slip events on the subducting plate boundary. Some of recent discoveries of new phenomena and advanced insights for crustal activities including large earthquakes are owing to these developments and organized networks for the monitoring of crustal deformation. Because the history of these observations is much shorter than the interval of large earthquakes, the continuation and development of the monitoring are important for further researches and understanding. In order to understand the crustal activities, it is also important to discriminate between tectonic and non-tectonic deformation induced by underground water and surface loads such as ocean and atmosphere in the observed signals.