In an artificial hip joint stem of the present invention, a distance between an inner wall portion and an outer wall portion is decreased as separating from an opening part in a sectional view that is parallel to a stem central axis and includes the inner wall portion and the outer wall portion, and both a front wall portion and a rear wall portion have a planar region in a sectional view that is parallel to the stem central axis and includes the front wall portion and the rear wall portion. A stem inserter of the present invention includes a disk-shaped front end part. The present invention also provides an artificial hip joint system including the artificial hip joint stem and the stem inserter, and an artificial hip joint including the artificial hip joint stem.
