The mounting of a coolant line system in a magnet device of an electric machine is to be simplified. Therefore, a magnet device is provided, with a ferromagnetic base member (4) comprising a first (3) and an opposite second side (5) and comprising penetration holes for coolant lines from the first side (3) to the second side (5), and a plurality of first coolant line segments (1) inserted through the holes. The first coolant line segments (1) are U-shaped and each of the free leg ends (2) thereof is inserted through two of the holes of the first side (3) such that the leg ends (2) protrude from the second side (5) of the base member (4). Two of the leg ends of the first coolant line segments (1) are connected by way of a second coolant line segment. Thus, only two types of coolant line segments are needed to construct the coolant line system, and also the coolant line segments can be connected at a single side (5) of the base member (4).