Physiologic pituitary enlargement is common during normal pregnancy. However, symptoms such as diplopia, blurred vision and headache resulting from physiologic pituitary enlargement are very rare during pregnancy. A 39-year-old woman complained of sudden diplopia and left eye ptosis at 33th weeks of gestation. An magnetic resonance imaging (MRI) demonstrated the pituitary enlargement compressing the optic chiasm. Notwithstanding the medication of bromocriptine, her symptoms did not regress during pregnancy. At 5 months after delivery, her symptoms dramatically resolved without any surgery, and her visual acuity was normalized. Her MRI scan also revealed more decreased size of pituitary gland compared to antenatal MRI. We report a case of visual loss due to the physiologic pituitary enlargement of nonfunctioning adenoma during pregnancy, which regressed spontaneously after delivery without any surgery.