An assembly manufacturing device, comprising: a plurality of first gripping parts that are configured to grip a first member having a long shape; a retaining part that is configured to retain a first end of the first member and to restrict movement of the first member in the longitudinal direction; a first driving part (9,12) that is configured to move the first gripping parts and to adjust a position of the first gripping parts that are configured to grip the first member; a detecting part that is configured to detect the installation position of the retaining part; a reference determining part for determining a reference point or reference coordinates used for adjusting the position of the first gripping part, based on the installation position of the retaining part detected by the detecting part; a storing part for storing an original shape of the first member; a control unit for driving the first driving part (9, 12) and adjusting the positions of the plurality of gripping parts that are configured to grip the first member, such that the shape of the first member gripped by the first gripping part matches the original shape, based on the original shape stored in the storage part and the reference coordinates or reference point determined by the reference determining part; and a first reflecting part that is configured to reflect laser light, provided on the retaining part; wherein the detecting part comprises: an irradiating part that is configured to irradiate laser light while scanning; a light receiving part that is configured to receive the laser light reflected by the first reflecting part; and a position calculating part that is configured to calculate an installation position of the retaining part on which the first reflecting part is provided, based on the laser light reflected by the first reflecting part and received by the light receiving part, the reference determining part is configured to determine the reference coordinates or reference point based on the installation position of the retaining part calculated by the position calculating part, the assembly manufacturing device being characterised in that: the position of the first reflecting part is set such that a positional error of the reference point determined by the reference determining part is smaller than a detection error of the detecting part. a plurality of first gripping parts that are configured to grip a first member having a long shape; a retaining part that is configured to retain a first end of the first member and to restrict movement of the first member in the longitudinal direction; a first driving part (9,12) that is configured to move the first gripping parts and to adjust a position of the first gripping parts that are configured to grip the first member; a detecting part that is configured to detect the installation position of the retaining part; a reference determining part for determining a reference point or reference coordinates used for adjusting the position of the first gripping part, based on the installation position of the retaining part detected by the detecting part; a storing part for storing an original shape of the first member; a control unit for driving the first driving part (9, 12) and adjusting the positions of the plurality of gripping parts that are configured to grip the first member, such that the shape of the first member gripped by the first gripping part matches the original shape, based on the original shape stored in the storage part and the reference coordinates or reference point determined by the reference determining part; and a first reflecting part that is configured to reflect laser light, provided on the retaining part; wherein the detecting part comprises: an irradiating part that is configured to irradiate laser light while scanning; a light receiving part that is configured to receive the laser light reflected by the first reflecting part; and a position calculating part that is configured to calculate an installation position of the retaining part on which the first reflecting part is provided, based on the laser light reflected by the first reflecting part and received by the light receiving part, the reference determining part is configured to determine the reference coordinates or reference point based on the installation position of the retaining part calculated by the position calculating part, the assembly manufacturing device being characterised in that: the position of the first reflecting part is set such that a positional error of the reference point determined by the reference determining part is smaller than a detection error of the detecting part. an irradiating part that is configured to irradiate laser light while scanning; a light receiving part that is configured to receive the laser light reflected by the first reflecting part; and a position calculating part that is configured to calculate an installation position of the retaining part on which the first reflecting part is provided, based on the laser light reflected by the first reflecting part and received by the light receiving part,