An apparatus is provided for collecting amniotic fluid from the uterus. In order to collect the amniotic fluid from the uterus through the external orifice of the cervix of a pregnant woman, an amniotic fluid collecting unit is adapted to bring a mouth, which is foldably formed at the upper end of an amniotic fluid collecting bag, into close contact with an end of the external orifice of the cervix. Thereby, the apparatus not only significantly decreases the risk occurring when a needle is directly inserted into the uterus in order to carry out the amniocentesis (amniotic fluid testing), but also eliminates pain and anxiety caused by the direct insertion of the needle.