A diagnosis image generation apparatus comprising: a low resolution image signal synthesis unit configured to synthesize each of a plurality of low resolution image signals, which correspond to a plurality of low resolution images, by using a signal reflected from a subject and received with a plurality of M transducers using Equation l i r p → = ∑ m = 0 M − 1 w * m, i r p → y m, i Δ m, i r p → where r p is a focal point of a received signal that is transmitted from the transducer and reflected from the subject, l i ( r p) is a size value of a signal corresponding to a pixel in a position r p of an i th low resolution image, w* m,i ( r p) is a beamforming coefficient that is applied to a pixel in the position r p among signal values corresponding to respective positions of pixels forming the i th low resolution image based on a signal received by an m th transducer, a superscript * is a conjugate complex number, y m,j () is a signal, received by the m th transducer, for the i th low resolution image, Δ m,j is a sampling time for signals, received by the m th transducer, for the i th low resolution image, and y m,i (Δ m,i ( r p)) is a signal that is obtained by applying a delay value to a pixel in the position r p for a signal, received by the m th transducer, for the i th low resolution image; a weight calculation unit configured to calculate a weight based on signal values for pixels of the low resolution images to be synthesized in a same position as a position of one pixel of a low resolution image to minimize variances between the signal values, the weight being calculated with respect to each of some pixels included in the respective low resolution images; and a high resolution image signal synthesis unit configured to synthesize high resolution image signals by applying the calculated weight to pixels included in a region including a pixel corresponding to the position in each of the low resolution images. a low resolution image signal synthesis unit configured to synthesize each of a plurality of low resolution image signals, which correspond to a plurality of low resolution images, by using a signal reflected from a subject and received with a plurality of M transducers using Equation l i r p → = ∑ m = 0 M − 1 w * m, i r p → y m, i Δ m, i r p → where r p is a focal point of a received signal that is transmitted from the transducer and reflected from the subject, l i ( r p) is a size value of a signal corresponding to a pixel in a position r p of an i th low resolution image, w* m,i ( r p) is a beamforming coefficient that is applied to a pixel in the position r p among signal values corresponding to respective positions of pixels forming the i th low resolution image based on a signal received by an m th transducer, a superscript * is a conjugate complex number, y m,j () is a signal, received by the m th transducer, for the i th low resolution image, Δ m,j is a sampling time for signals, received by the m th transducer, for the i th low resolution image, and y m,i (Δ m,i ( r p)) is a signal that is obtained by applying a delay value to a pixel in the position r p for a signal, received by the m th transducer, for the i th low resolution image; a weight calculation unit configured to calculate a weight based on signal values for pixels of the low resolution images to be synthesized in a same position as a position of one pixel of a low resolution image to minimize variances between the signal values, the weight being calculated with respect to each of some pixels included in the respective low resolution images; and a high resolution image signal synthesis unit configured to synthesize high resolution image signals by applying the calculated weight to pixels included in a region including a pixel corresponding to the position in each of the low resolution images.