We fabricated epi pn diodes and investigated the correlation between defects included in the 4H-SiC epilayers and the leakage current of the pn diodes. Threading edge dislocations, screw dislocations, basal plane dislocations and in-grown stacking faults existed in the epilayers. From EL images of the diodes under reverse bias voltage, it was found that a line of edge dislocations forming a grain boundary and some screw dislocations caused an increase in leakage current. We also mention the influence of dissociated micropipes.