The subcutaneous penetrating instrument (1) for guiding a catheter is provided with: a rod-shaped body section (2) a sloped flat section (3), which is provided at one end (21) of the rod-shaped body section (2) and is formed with a slant of a specified angle with respect to the rod-shaped body section (2) and a flat section sloped surface recognition marker, which is provided at a position that is a specified distance from the sloped flat section (3), in other words, a position that is closer to the base end of the rod-shaped body section (2) than the sloped flat section (3) by a specified distance, and on the surface that is in the direction that the sloped flat section (3) slopes and which can be confirmed by touch. The sloped flat section (3) also has: a catheter insertion/holding part, which is provided so as to pass through the sloped surface of the sloped flat section (3), into which a catheter can be inserted, and which is for holding the inserted catheter and an end (6) for insertion into a living body, the end having a rounded overall shape.
