It is an objective of the present invention to provide an indexable insert for drilling, which can constantly maintain the shape of a cutting edge at the central cutting region in spite of indexing, and a blank insert for manufacturing such an indexable insert. To achieve the above objective, the present invention provides an indexable insert for drilling, which comprises: front and rear edges opposite to each other and having a rotationally symmetrical relation; and two side surfaces opposite to each other and having a rotationally symmetrical relation. Each side surface has first and second cutting edge portions formed thereon. The first cutting edge portion is disposed farther than the second cutting edge from the center of the blank insert, thereby providing a step between the first and second cutting edge. The first cutting edge is adjacent to the front edge.