To provide a guide attachment of an electric drill with which boring work can be guided on a target to be bored and a boring depth adjusted during the boring work does not vary.

The guide attachment 5 of the electric drill 3 having a drill bit 2 mounted for guiding the boring work on the target C to be bored includes a nested slide guide 53 comprising a guide holder 51 mounted on the electric drill 3 coupled with a nose block 52 having an insertion opening 61 to which the drill bit 2 is inserted and pushed against the target C. The slide guide 53 comprises a first guide cylinder 70 having one of ends fixed to the nose block 52 and a first guide rod 71 having one of ends screwed with the guide holder 51 which are slidably coupled. The first guide rod 71 has its sliding end position on a contraction side regulated in position by fitting, and also forms an adjustment screw mechanism AS by screwing with the guide holder 51.