A drilling device drilling to a desired depth without a gauge. The drilling device includes a distance sensor positioned on an imaginary line spanning between a front end of the housing and a hand gripped portion. The distance sensor is away form a front end of a gear housing by a distance Ls. The distance sensor provides an effective measurement range. The relationship of L1≦Ls and Ls+Lb≦L2 is satisfied where L1 represents a distance between the distance sensor and a point closest to the distance sensor and defining a lower limit of the effective measurement range, L2 represents a distance between the distance sensor and a point farthest from the distance sensor and defining an upper limit of the effective measurement range, and Lb represents a distance between the front end of the housing and a tip end of the end bit.