In this paper, the cosmic microwave background (CMB) anisotropy in a multiply connected compact flat 3-torus model with the cosmological constant is investigated. Using the COBE-DMR four-year data, a full Bayesian analysis revealed that the constraint on the topology of the flat 3-torus model with low matter density is less stringent. As in compact hyperbolic models, the large-angle temperature fluctuations can be produced as the gravitational potential decays at the Λ-dominant epoch well after the last scattering. The maximum allowed number of images of the cell, N (fundamental domain), within the observable region at present is approximately 49 for Ω_m = 0.1 and Ω_Λ = 0.9, whereas N~8 for Ω_m = 1.0 and Ω_Λ = 0.