A hydraulic shock absorber comprising: an oil chamber of a cylinder provided in a damper case which is attached to one of a vehicle body side and an axle side; a piston rod attached to another of the vehicle body side and the axle side, the piston rod being inserted into the oil chamber; a piston provided in a leading end portion of the piston rod, the oil chamber of the cylinder being divided into a piston side oil chamber and a rod side oil chamber by the piston; an oil reservoir chamber compensating a volumetric capacity of the piston rod which goes into and out of the oil chamber of the cylinder, the oil reservoir chamber being communicated with the oil chamber of the cylinder; and a damping force generating device provided between the piston side oil chamber and the rod side oil chamber of the cylinder; wherein an outer flow path communicating between the piston side oil chamber and the rod side oil chamber is provided around the oil chamber of the cylinder in the damper case, the oil reservoir chamber is provided around the oil chamber and the outer flow path of the cylinder in the damper case. and wherein the damping force generating device is provided with a compression side flow path (46A, 46B, 50A, 60B) which circulates the oil in the piston side oil chamber of the cylinder toward the rod side oil chamber via the outer flow path of the cylinder in a compression side stroke, the compression side flow path (46A, 46B, 50A, 60B) is provided with a compression side damping valve in its upstream side and with a compression side check valve in its downstream side, and an intermediate portion of the compression side damping valve and the compression side check valve in the compression side flow path (46A, 46B, 50A, 60B) is communicated with the oil reservoir chamber, and the damping force generating device is provided with an extension side flow path (46A, 46B, 50B, 60A) which circulates the oil in the rod side oil chamber of the cylinder toward the piston side oil chamber via the outer flow path of the cylinder in an extension side stroke, the extension side flow path (46A, 46B, 50B, 60A) is provided with an extension side damping valve in its upstream side and with an extension side check valve in its downstream side, and an intermediate portion of the extension side damping valve and the extension side check valve in the extension side flow path (46A, 46B, 50B, 60A) is communicated with the oil reservoir chamber, characterized in that the damping force generating device is provided in the state of a sub-assembled valve unit, wherein the damping force generating device is accessorily provided with a compression side damping force generating means in the compression side check valve provided in the downstream side of the compression side flow path (46A, 46B, 50A, 60B), and wherein the damping force generating device is accessorily provided with an extension side damping force generating means in the extension side check valve provided in the downstream side of the extension side flow path (46A, 46B, 50B, 60A). an oil chamber of a cylinder provided in a damper case which is attached to one of a vehicle body side and an axle side; a piston rod attached to another of the vehicle body side and the axle side, the piston rod being inserted into the oil chamber; a piston provided in a leading end portion of the piston rod, the oil chamber of the cylinder being divided into a piston side oil chamber and a rod side oil chamber by the piston; an oil reservoir chamber compensating a volumetric capacity of the piston rod which goes into and out of the oil chamber of the cylinder, the oil reservoir chamber being communicated with the oil chamber of the cylinder; and a damping force generating device provided between the piston side oil chamber and the rod side oil chamber of the cylinder; wherein an outer flow path communicating between the piston side oil chamber and the rod side oil chamber is provided around the oil chamber of the cylinder in the damper case, the oil reservoir chamber is provided around the oil chamber and the outer flow path of the cylinder in the damper case. and wherein the damping force generating device is provided with a compression side flow path (46A, 46B, 50A, 60B) which circulates the oil in the piston side oil chamber of the cylinder toward the rod side oil chamber via the outer flow path of the cylinder in a compression side stroke, the compression side flow path (46A, 46B, 50A, 60B) is provided with a compression side damping valve in its upstream side and with a compression side check valve in its downstream side, and an intermediate portion of the compression side damping valve and the compression side check valve in the compression side flow path (46A, 46B, 50A, 60B) is communicated with the oil reservoir chamber, and