Orbital ordering is the ordered state of orbital, which is independent of spin ordering. And it can be interpreted as the deviation of charge distribution in the crystal. It was considered that degrees of freedom in charge and spin affect the physical property. After the middle of 1990's, study for strongly correlated electron system made it clear that degrees of freedom in charge, spin and orbital affect the physical properties. Now, earnest study on this field is performed in the viewpoint of theory and experiment.