A back stretching device includes a handle unit including two parallel handgrip units. A support unit includes a lower cross bar connecting between front ends of the two handgrip tubes. A hold-down unit includes two parallel guide rods and an upper cross bar connecting between upper ends of the guide rods and parallel to the lower cross bar. The adjustment unit couples the guide rods to the handgrip tubes to define a distance-adjustable constraint space between the upper and lower cross bars. The constraint space receives the legs of a user to extend therethrough in a closely juxtaposed manner with the lower cross bar supporting the underside of the legs and with the upper cross bar constraining the upper side of the legs. The hands of the user are allowed to hold the two handgrip tubes to support the legs and body of the user for carrying out a desired stretching and exercise operation.