To provide a continuous-placement horizontal drilling method for making continuous-placement horizontal drilling possible, so far impossible in prior arts, using a cable with a reusable pipe as a component for retaining cable strength.

In horizontal drilling a cable 1 is needed, which consists of a pipe, a water supply pipe, a communication line and a feeding line formed of iron, steel or other materials for retaining strength. The pipe formed of iron, steel or other materials for retaining strength is formed of a long iron member or a multi-coiled foil to be stored in a drum on a vehicle in the range of elasticity enough for reuse.