A support structure, which includes: a housing configured to store an optical element; a support unit configured to support the housing; a positioning element configured to position the housing with respect to the support unit; a vibration-proof element configured to prevent transmission of vibration from the support unit to the housing; and an extension from the housing toward the support unit. The support unit includes a first surface configured to define an opening into which the extension is inserted. The positioning element supports and positions the extension in the opening so that the extension portion is apart from the first surface. The vibration-proof element is disposed between the first surface and the extension portion.