Provide a mechanical seal device with improved seal cover structure that achieves excellent ease of handling the seal ring or other seal element during maintenance. A mechanical seal device having a mating ring (131) that rotates with a rotating shaft (101), as well as an opposing seal ring (133) that slidably contacts the mating ring (131), so as to seal between the rotating shaft (101) and a seal cover (105) fixed to an equipment main body (102); wherein such mechanical seal device is characterized in that the seal cover (105) is a split structure comprising at least a first seal cover (107, 108) and second seal cover (106), the first seal cover (107, 108) is detachably connected in the axial direction by leaving the second seal cover (106) free from it, and the seal ring (133) is connected to the first seal cover (107, 108) in a securely following manner.