To investigate the choroidal vascular structural changes in eyes with central serous chorioretinopathy (CSC) by using swept-source optical coherence tomography (SS-OCT). Prospective cross-sectional study. We prospectively examined 40 eyes of 34 consecutive patients with CSC. Three-dimensional choroidal images of the macular area, covering 3×3mm and 6× 6mm, were obtained with SS-OCT. En face images of the microvasculature of the inner choroid and large choroidal vessel layers were converted to binary images. Choroidal vascular areas were analyzed quantitatively using the binary images. The choroidal vascular area was larger in eyes with CSC (the microvasculature of the inner choroid: 53.4% ± 2.4%, P= .028; 3× 3-mm large choroidal vessels: 66.9% ± 7.1%, P < .001; and 6× 6-mm large choroidal vessels: 64.8% ± 7.3%, P< .001) than in age-matched normal eyes (52.2% ± 1.8%, 54.9% ± 4.4%, and 53.8% ± 4.3%, respectively). The choroidal vascular area at the microvasculature of the inner choroid level was larger in multifocal posterior pigment epitheliopathy (55.8% ± 2.2%) than in classic CSC (53.1% ± 2.1%, P=.038) and in diffuse retinal pigment epitheliopathy (52.9% ± 2.6%, P= .042). The subfoveal choroidal thickness was significantly associated with the choroidal vascular area at the level of large choroidal vessels (P < .001). Increased choroidal vascular area was observed in the whole macula area in eyes with CSC. This finding suggests that CSC may originate from a choroidal circulatory disturbance.