A fluid temperature control device for an extracorporeal blood treatment apparatus, comprises: a casing (26) delimiting a heating seat (20) configured to accommodate a fluid warming bag (17) connected or connectable to an extracorporeal blood treatment apparatus (1)； heating elements (29, 30) operatively active in the heating seat (20) to heat the fluid warming bag (17)； at least a presence detector (32, 33) operatively active in the heating seat (20) to detect the presence of the fluid warming bag (17). The presence detector (32, 33) comprises an electromagnetic transmitter (34) and an electromagnetic receiver (35). The electromagnetic receiver (35) is positioned with respect to the electromagnetic transmitter (34) either to receive an electromagnetic radiation emitted by the electromagnetic transmitter (34) and reflected by the fluid warming bag (17) only when the fluid warming bag (17) is properly accommodated in the heating seat (20) or only when the fluid warming bag (17) is not properly accommodated in the heating seat (20).
