An inside-type mechanical seal comprising a sleeve fixed to a rotating shaft, and a cartridge fixed to a housing; a rotation-side sealing ring being provided to said sleeve; and a fixed-side sealing ring, which slides against said rotation-side sealing ring, and a bellows for axially urging the fixed-side sealing ring, being provided to said cartridge; the mechanical seal being characterized in that: said bellows is made from a metal; the plate thickness of said metal bellows being set so as to be smaller than the plate thickness of said case or said cartridge; said sleeve has an inner cylinder part fitted to said rotating shaft, a disc part extending in the outer diameter direction from the high-pressure-fluid side of the inner cylinder part; and an outer cylinder part extending from the outer diameter side of the disc part to the low-pressure-fluid side, said sleeve supports said rotation-side sealing ring to the low-pressure-fluid side having a substantially C-shaped cross-section via a cup gasket, said cup gasket is provided across the side opposite the sealing face of the rotation-side sealing ring, a distal end of the inner cylinder part of said sleeve is expanded in diameter by crimping and caused to engage with an inner cylinder part of said cartridge, thereby preventing said cartridge and said sleeve from axial detachment; characterised in that: said metal bellows has one end fixed to a case for holding said fixed-side sealing ring and another end fixed to said cartridge; said cup gasket is also provided across the outer circumferential surface of the rotation-side sealing ring; a portion of the inner cylinder part of said cartridge located on the opposite axial-direction side relative to said fixed-side sealing ring is expanded in diameter and provided with a stepped part; and said bellows is formed so that the inner diameter of a portion positioned on the fixed-side sealing ring side relative to the stepped part of the inner cylinder part of said cartridge is smaller than the inner diameter of a portion positioned on the opposite side from the fixed-side sealing ring relative to the stepped part of the inner cylinder part of said cartridge. said bellows is made from a metal; the plate thickness of said metal bellows being set so as to be smaller than the plate thickness of said case or said cartridge; said sleeve has an inner cylinder part fitted to said rotating shaft, a disc part extending in the outer diameter direction from the high-pressure-fluid side of the inner cylinder part; and an outer cylinder part extending from the outer diameter side of the disc part to the low-pressure-fluid side, said sleeve supports said rotation-side sealing ring to the low-pressure-fluid side having a substantially C-shaped cross-section via a cup gasket, said cup gasket is provided across the side opposite the sealing face of the rotation-side sealing ring, a distal end of the inner cylinder part of said sleeve is expanded in diameter by crimping and caused to engage with an inner cylinder part of said cartridge, thereby preventing said cartridge and said sleeve from axial detachment; characterised in that: said metal bellows has one end fixed to a case for holding said fixed-side sealing ring and another end fixed to said cartridge; said cup gasket is also provided across the outer circumferential surface of the rotation-side sealing ring; said metal bellows has one end fixed to a case for holding said fixed-side sealing ring and another end fixed to said cartridge; said cup gasket is also provided across the outer circumferential surface of the rotation-side sealing ring; a portion of the inner cylinder part of said cartridge located on the opposite axial-direction side relative to said fixed-side sealing ring is expanded in diameter and provided with a stepped part; and said bellows is formed so that the inner diameter of a portion positioned on the fixed-side sealing ring side relative to the stepped part of the inner cylinder part of said cartridge is smaller than the inner diameter of a portion positioned on the opposite side from the fixed-side sealing ring relative to the stepped part of the inner cylinder part of said cartridge.