A mechanical seal device has a mating ring that rotates with a rotating shaft, as well as a seal ring that slidably contacts the mating right, so as to seal between the rotating shaft and a seal cover fixed to an equipment main body, wherein the seal cover is a split structure comprising at least an inner-diameter-side seal cover and an outer-diameter-side seal cover, the inner-diameter-side seal cover is detachably connected to the outer-diameter-side seal cover, and the seal ring is connected to the inner-diameter-side seal cover in a securely following manner.