Although it is necessary to handle the errors in order to successfully operate quantum algorithms, there are still many technical limitations on the implementation of fault tolerance. Error mitigation is a method of estimating ideal values using the results from many slightly different versions of a target algorithm, which overcomes the technical limitations and will be of great help in the near future NISQ era. In this talk, I will introduce the basics and some typical examples of quantum error mitigation such as Zero-noise extrapolation(ZNE), Probabilistic error cancellation(PEC), and Measurement error mitigation.