An assembling apparatus configured to mount a first part on a second part having an engaged part extending in a first direction includes a holding part configured to hold the first part, an engaging part extending in the first direction and being configured to engage with the engaged part, a support part configured to support the holding part and the engaging part, a first mechanism configured to displace the support part in the first direction, and a second mechanism configured to allow a displacement of the support part in a plane intersecting with the first direction.