The effects of magnetic fields (MFs) on the corrosion of 304 stainless steel (SS304) caused by oil-field sulfatereducing bacteria (SRB) were investigated. Experimental data showed that the MF lowered the population of planktonic SRB by almost 4 orders of magnitude and delayed the formation of SRB biofilms on the SS304 coupons. The mass losses and surface images of the coupons indicated that the application of an MF considerably reduced the pitting corrosion of SS304. EDX and XPS analyses of the coupon surfaces demonstrated that the main corrosion products without an MF and with 2 and 4 mT MFs were FeS, FeO, and Fe2O3, respectively. The application of MFs could be an environmentally friendly method for mitigating microbiologically influenced corrosion (MIC) on SS304.