An imaging apparatus for diagnosis adapted to reconfigure a three-dimensional image of a blood vessel including a probe adapted to emit light toward a vascular lumen surface, said probe accommodating an imaging core adapted to detect reflection light therefrom, to move the imaging core along the probe at a predetermined speed while the imaging core is rotated, the apparatus comprising: deriving means adapted to derive line data configured to include multiple luminance values arrayed side by side in a radial direction from the rotation center of the imaging core per each rotation angle (θ) in the rotation, based on data obtained by the imaging core during a period while the imaging core is rotated and moved; calculation means adapted to calculate a two-dimensional image data in which θ, z are set to two axes, by calculating a representative pixel value P (θ, z) in a viewing direction toward the radial direction from the rotation center of the imaging core in each line data L (θ, z), when the rotation angle (θ) of the imaging core is defined as θ and the line data at a movement position z in the movement is defined as L (θ, z); and display means adapted to display the calculated two-dimensional image data, the calculation means further including: generation means adapted to generate three-dimensional model data of the blood vessel, based on each line data obtained by the deriving means; discrimination means adapted to discriminate whether or not each line data obtained by the deriving means is line data indicating a stent indwelling the blood vessel; characterized in that the calculation means further includes: specifying means adapted to specify a portion where a malapposition having a predetermined threshold value or greater is present between a vascular lumen surface and a surface of the stent opposing the vascular lumen surface, based on the discrimination result obtained by the discrimination means, the three-dimensional model data obtained by the generation means, and a preset thickness d of the stent; representative pixel value calculation means adapted to calculate the representative pixel value of the line data by converting a luminance value of each line data into a value indicating opacity using a preset conversion function, and by continuously adding the value indicating the opacity of a luminance value along the radial direction from the center position of the rotation; and correction means adapted to correct a pixel value corresponding to a portion specified by the specifying means within image data configured to have the representative pixel value calculated by the representative pixel value calculation means, and to generate the two-dimensional image data for highlighting the portion where the malapposition is present. deriving means adapted to derive line data configured to include multiple luminance values arrayed side by side in a radial direction from the rotation center of the imaging core per each rotation angle (θ) in the rotation, based on data obtained by the imaging core during a period while the imaging core is rotated and moved; calculation means adapted to calculate a two-dimensional image data in which θ, z are set to two axes, by calculating a representative pixel value P (θ, z) in a viewing direction toward the radial direction from the rotation center of the imaging core in each line data L (θ, z), when the rotation angle (θ) of the imaging core is defined as θ and the line data at a movement position z in the movement is defined as L (θ, z); and display means adapted to display the calculated two-dimensional image data, the calculation means further including: generation means adapted to generate three-dimensional model data of the blood vessel, based on each line data obtained by the deriving means; discrimination means adapted to discriminate whether or not each line data obtained by the deriving means is line data indicating a stent indwelling the blood vessel; characterized in that the calculation means further includes: specifying means adapted to specify a portion where a malapposition having a predetermined threshold value or greater is present between a vascular lumen surface and a surface of the stent opposing the vascular lumen surface, based on the discrimination result obtained by the discrimination means, the three-dimensional model data obtained by the generation means, and a preset thickness d of the stent; representative pixel value calculation means adapted to calculate the representative pixel value of the line data by converting a luminance value of each line data into a value indicating opacity using a preset conversion function, and by continuously adding the value indicating the opacity of a luminance value along the radial direction from the center position of the rotation; and correction means adapted to correct a pixel value corresponding to a portion specified by the specifying means within image data configured to have the representative pixel value calculated by the representative pixel value calculation means, and to generate the two-dimensional image data for highlighting the portion where the malapposition is present.