Iron-based superconductors were discovered in 2008 as the second series of high-T_c superconductors. These materials have the layered structure, which is similar to cuprate superconductors. However, the pairing mechanism is considered to be different from each other. For iron-based superconductors, the pressure dependences of Tc are significantly large. It is indicated that the electronic property of these materials is very sensitive to the local structure around Fe atom from the extensive experimental and theoretical studies. Then it may be possible that the large pressure effects for superconducting properties are due to the high sensitivity of the local structure to the pressure. In this manuscript, the recent results of electrical and structural studies under high pressure are reported. The recent developments of high pressure technique including thermal measurements are also introduced.