Aim: To compare the effects of intravitreal bevacizumab on different morphologic patterns of diabetic macular edema (DME) classified using optical coherence tomography (OCT). Materials and Methods: Medical records for 65 eyes of 48 patients were retrospectively reviewed, and each subject was classified as one of three DME types according to the OCT features: diffuse retinal thickening (DRT), cystoid macular edema (CME), serous retinal detachment (SRD). Subjects were given three monthly intravitreal injections of bevacizumab (1.25 mg/0.05 ml). The clinical course of best-corrected visual acuity (BCVA) with a logarithm of the minimum angle of resolution chart and central foveal thickness (CFT) using OCT was monitored for 12 months after the injections. On follow-up, injections were repeated if DME remained or was aggravated. Results: Of the 65 eyes with DME, 29 eyes were of the DRT type, 21 of the CME type, and 15 of the SRD type. Before the injection, CFT and BCVA were, respectively, 377.1 ± 145.9 µm and 0.54 ± 0.36 in the DRT type, 427.7 ± 143.1 µm and 0.59 ± 0.42 in the CME type, and 485.1 ± 187.1 µm and 0.65 ± 0.27 in the SRD type; there was no significant difference in CFT and BCVA between DME types (p > 0.05). At 6 months, the changes in BCVA and CFT differed significantly between OCT types (p < 0.05). At 12 months, changes in CFT and BCVA from baseline were not significantly different between groups (p > 0.05). The DRT type was associated with a greater reduction in the CFT and greater BCVA improvement than the CME or SRD types. Conclusions: Three monthly injections of intravitreal bevacizumab seem to be effective treatment in the first 6 months, but the therapeutic effect is temporary and repeated injections of bevacizumab should be considered to maintain the therapeutic effect after 6 months. In addition, intravitreal injection of bevacizumab was more effective in the DRT type than in the CME or SRD types of DME.