An insertion apparatus includes an insertion section including a flexible tube section configured to passively bend, and a bendable section connected to the flexible tube section on a distal end side and configured to actively change its bend shape, and a characteristic changer provided in the flexible tube section and configured to change a force quantity acting on a distal end of the insertion section from an insertion target body. The apparatus also includes an analyzer configured to calculate information relating to a deformation force quantity that restores bending of the insertion section on the proximal end side of the changer, and a controller configured to control the changer based on the information relating to the deformation force quantity.
