A cable protecting tube having high transparency and allowing the filling condition of mortar therein to be visually observed from the outside as well as exhibiting high pressure resistance is provided. A cable protecting tube for accommodating a cable and for filling with mortar includes a protecting tube (1) having smooth inner and outer surfaces formed from an ionomer resin excellent in transparency, and a spiral or mesh-shaped reinforcing member (2) for reinforcing the protecting tube. The reinforcing member (2) may be buried in the protecting tube (1). The protecting tube (1) is not limited to the smooth-walled tube but may be a spirally corrugated tube.