To provide an insert for a rotary cutting tool which can reduce the cutting resistance while sufficiently ensuring the strength of a blade tip.

A nose part is formed on a corner part of the substantially parallelogram plate-like insert, and a long side cutting blade and a short side cutting blade are formed on a ridge part formed by a pair of flanks adjacent to each other across the nose part and an upper surface including the nose part. The long side cutting blade has a cutting blade inclined in the bottom surface direction as being separated from the nose part, the long side cutting blade has a projecting cutting blade in a range of 1/2 to 3/4 of the total length of the long side cutting blade from the nose part, and a remaining portion of the long side cutting blade has a straight cutting blade.