[en] Full text: The JENDL-4.0 was released in March 2010. It provides neutron nuclear data for 79 actinides from Ac to Fm. All of the actinides include covariance data. The covariance data were evaluated for reaction cross sections, resonance parameters, angular distributions of elastic scattering, average number of neutrons per fission, and prompt fission neutron spectra. They were deduced basically based on the consistent methodologies with the nuclear data evaluations. Statistical processing of experimental data sometimes gives unacceptably small uncertainty compared with experimental data. They may arise from ignoring unknown errors and correlation of experimental data and also from the modeling errors. The covariance data obtained from statistical estimation using the least-squares method were sometimes modified to be reasonable taking account of consistency with dispersion of experimental data, which may reflect the uncertainties of the data. For the fast neutron fission cross sections of 6 major actinides of ^233,235,238U and ^239,240,241Pu were evaluated simultaneously using both cross section and their ratio data with the least- squares fitting code SOK. It gave the covariance matrices that have cross correlations between different nuclei included in the analyses. For the minor actinide, the least-squares fitting code GMA was used for fission cross section evaluation for fast neutrons. The covariance data were obtained from the calculations at the same time. For other reaction cross sections, covariance matrices were evaluated using CCONE-KALMAN code system. Sensitivities to model parameters were calculated by CCONE code and used to estimate covariance matrices of the parameters with KALMAN code. Covariance matrices for other data such as resonance parameters and average numbers of fission neutrons were also evaluated based on experimental data. The evaluated covariance data were compiled to the ENDF-6 format files and included in JENDL-4.