A slide rail assembly, comprising: a first rail; a second rail longitudinally movable relative to the first rail; a blocking structure arranged on the first rail; a base connected to the second rail; and a fitting member detachably mounted to the second rail, the fitting member being an adjusting device; wherein the adjusting device comprises a mounting member and an adjusting member, the adjusting member comprises a head portion connected to a body portion and a size of the head portion is greater than a size of the body portion, the mounting member comprises a first threaded feature, the mounting member and the adjusting member are connected to each other in an adjustable manner, so that the position of the adjusting member may be adjusted relative to the mounting member such that the longitudinal length of the adjusting device is adjustable, the mounting member is able to be mounted on the base, the adjusting member abuts against the blocking structure when the second rail is retracted relative to the first rail; wherein when the adjusting member is screwed through a second threaded feature to the first threaded feature of the mounting member, the head portion is located out of a space S of the base; wherein the mounting member is accommodated in said space S of the base; wherein when the adjusting member is rotated clockwise or counterclockwise, the adjusting device is adjusted to extend the base by different lengths; wherein when the adjusting device is mounted to the second rail and the second rail is retraced relative to the first rail, through the adjusting device abutting against the blocking structure allows the second rail to be located at one single longitudinally predetermined position or multiple longitudinally predetermined positions relative to the first rail; wherein the adjusting device is detachably mounted on the base. a first rail; a second rail longitudinally movable relative to the first rail; a blocking structure arranged on the first rail; a base connected to the second rail; and a fitting member detachably mounted to the second rail, the fitting member being an adjusting device; wherein the adjusting device comprises a mounting member and an adjusting member, the adjusting member comprises a head portion connected to a body portion and a size of the head portion is greater than a size of the body portion, the mounting member comprises a first threaded feature, the mounting member and the adjusting member are connected to each other in an adjustable manner, so that the position of the adjusting member may be adjusted relative to the mounting member such that the longitudinal length of the adjusting device is adjustable, the mounting member is able to be mounted on the base, the adjusting member abuts against the blocking structure when the second rail is retracted relative to the first rail; wherein when the adjusting member is screwed through a second threaded feature to the first threaded feature of the mounting member, the head portion is located out of a space S of the base; wherein the mounting member is accommodated in said space S of the base; wherein when the adjusting member is rotated clockwise or counterclockwise, the adjusting device is adjusted to extend the base by different lengths; wherein when the adjusting device is mounted to the second rail and the second rail is retraced relative to the first rail, through the adjusting device abutting against the blocking structure allows the second rail to be located at one single longitudinally predetermined position or multiple longitudinally predetermined positions relative to the first rail; wherein the adjusting device is detachably mounted on the base.