Position measuring system for measuring the relative position of a first machine part relative to a second machine part in a measurement direction, having - a carrier of a measuring scale division, which carrier can be mounted on the first machine part, - a scanning head for scanning the measuring scale division, which scanning head can be mounted on the second machine part, - a mounting aid by means of which the carrier of the measuring scale division is fastened to the scanning head in a mounting position, such that the carrier of the measuring scale division and the scanning head can be handled as a common unit and can be mounted in this assignment onto the machine parts (8, 9), wherein the mounting aid - has a first section, which, for the mounting, is fixed in a positionally static manner, and after the mounting has been performed, is fixed detachably, to the carrier of the measuring scale division, and - has a second section, which, for the mounting, is fixed in a positionally static manner, and after the mounting has been performed, is fixed detachably, to the scanning head, characterized in that - the mounting aid has at least one alignment device (4, 5) between the first section and the second section, which alignment device is designed such that the mounting position between the carrier of the measuring scale division relative to the scanning head is adjustable in at least one linear degree of freedom (X, Y) which deviates from the measurement direction, and that the at least one alignment device (4, 5) has an arrangement of multiple deflectable links (42 to 45, 52 to 55, 46 to 49) and an adjusting element (41, 51). - a carrier of a measuring scale division, which carrier can be mounted on the first machine part, - a scanning head for scanning the measuring scale division, which scanning head can be mounted on the second machine part, - a mounting aid by means of which the carrier of the measuring scale division is fastened to the scanning head in a mounting position, such that the carrier of the measuring scale division and the scanning head can be handled as a common unit and can be mounted in this assignment onto the machine parts (8, 9), wherein the mounting aid - has a first section, which, for the mounting, is fixed in a positionally static manner, and after the mounting has been performed, is fixed detachably, to the carrier of the measuring scale division, and - has a second section, which, for the mounting, is fixed in a positionally static manner, and after the mounting has been performed, is fixed detachably, to the scanning head, characterized in that - the mounting aid has at least one alignment device (4, 5) between the first section and the second section, which alignment device is designed such that the mounting position between the carrier of the measuring scale division relative to the scanning head is adjustable in at least one linear degree of freedom (X, Y) which deviates from the measurement direction, and that the at least one alignment device (4, 5) has an arrangement of multiple deflectable links (42 to 45, 52 to 55, 46 to 49) and an adjusting element (41, 51). - has a first section, which, for the mounting, is fixed in a positionally static manner, and after the mounting has been performed, is fixed detachably, to the carrier of the measuring scale division, and - has a second section, which, for the mounting, is fixed in a positionally static manner, and after the mounting has been performed, is fixed detachably, to the scanning head, characterized in that - the mounting aid has at least one alignment device (4, 5) between the first section and the second section, which alignment device is designed such that the mounting position between the carrier of the measuring scale division relative to the scanning head is adjustable in at least one linear degree of freedom (X, Y) which deviates from the measurement direction, and that the at least one alignment device (4, 5) has an arrangement of multiple deflectable links (42 to 45, 52 to 55, 46 to 49) and an adjusting element (41, 51).