A magazine for bundles of blanks includes a vertical channel configured for inserting and extracting bundles of blanks and a succession of groups of supporting parts distributed along the channel. The supporting parts are configured to support the underside of a respective bundle of blanks. More specifically, each supporting part is movable between an extracted position, where it projects from the channel, towards the inside of the channel, to intercept a bundle that is moving down along the channel and to provide a steady support for the bundle, and a retracted position, where the supporting part is aligned or recessed with respect to the channel to allow the bundle to move along the channel towards a portion under the supporting part. The magazine also includes, for each supporting part, an actuating device configured to promote the passage of the supporting part from the retracted position to the extracted position and controllable by an operator, preferably manually.