A mandrel mill a method for manufacturing a seamless pipe by using the mandrel mill includes a plurality of roll stands in which three grooved rolls R are disposed in each roll stand such that an angle formed by pressing directions is 120° and the pressing directions of the grooved rolls R are alternately shifted by 60° between adjacent roll stands, wherein a central angle θ defining a circular arc that constitutes a groove bottom profile of the grooved roll R disposed at least in the first and second roll stands is set at less than 60°. The mandrel mill can adequately suppress the problem of the mandrel bar not being able to be pulled out from a pipe after drawing and rolling, without resulting in an increase in facility cost and deterioration of maintainability.