Pregnancy with amyotrophic lateral sclerosis (ALS) is rare and generally considered dangerous. Riluzole is the only drug approved for use in ALS, but the effect on maternal and fetal health is unknown. We describe the case of an ALS patient taking riluzole throughout pregnancy. A 34-year old Japanese woman, who had been diagnosed with probable ALS 4 years earlier, visited our hospital for abdominal distension, without knowing that she was pregnant. The patient had been taking riluzole for 2 years, inclusive of her gestational months, and we decided to continue administration of the medication. The patient delivered a normal female infant transvaginally at 38 weeks gestation. The patient's neurological status was stable 1 year after delivery and the baby had developed normally. We found that, in this case, riluzole did not cause any side-effects to the pregnant woman or her fetus.