An illumination optical apparatus and a projection type display apparatus
capable of preventing an image on boundary lines of a fly-eye lens from
deviating from a designed position and preventing unevenness of
brightness is provided: wherein a first lens holding member holding said
first fly-eye lens; a second lens holding member joined to said first
lens holding member, and holding said second fly-eye lens; and a third
lens holding member joined to said second lens holding member, and
holding an optical lens are provided; and said first lens holding member
and said second lens holding member are joined to be relatively rotatable
about an optical axis.