We previously introduced the simplified sampling biorthogonal direction implicit (SSB-ADI) method for 2-D Maxwell's equations. This paper extends it to a 3-D SSB-ADI method. Similar to the original method, the 3-D SSB-ADI method also partially uses the sampling property and compact support of the SBTD algorithm to display spatial discretization. Dispersion and stability analysis are presented. A numerical example shows that the SSB-ADI method is superior to the SB-ADI method in terms of reducing the CPU time and memory requirement of the numerical simulation.