Abstract: In an automatic tool change system in a combined machining lathe, with rotational and planar movements of a tool change arm, tools are replaced with each other between magazine pots and first and second tool holders which are mounted to a turret so as to be directed to a rotation axis direction of the turret and to a rotation plane direction of the turret, respectively. A tool grasp part of the tool change arm includes first holding claws for inserting and withdrawing a tool into and from the first tool holder and second holding claws for inserting and withdrawing a tool into and-from the second tool holder. At a tool exchange position, each magazine pot is pivoted between a first exchange position where the magazine pot takes an attitude parallel to the first tool holder and a second exchange position where the magazine pot takes an attitude face to face with the second tool holder.