Photon counting device, photon counting method, and photon counting processing program

A photon counting device includes: a plurality of pixels including a photoelectric conversion element and an amplifier that amplifies and converts a charge converted by the photoelectric conversion element into a voltage; an A/D converter that converts the voltages output from the amplifiers of the plurality of pixels into digital values; a first derivation unit that derives, on the basis of the digital values, a provisional value of the number of photons for each of the plurality of pixels; and a second derivation unit that derives a determination value of the number of photons in the target pixel on the basis of a first probability based on the distribution of the number of photons and a second probability based on the readout noise. 光子计数装置具备：多个像素，包括光电转换元件和将由光电转换元件转换的电荷放大并转换为电压的放大器；A/D转换器，将从多个像素的放大器输出的电压转换为数字值；第一导出部，基于数字值，导出多个像素中的各像素的光子数的暂定值；和第二导出部，根据基于光子数分布的第一概率和基于读出噪声的第二概率，导出对象像素中的光子数的确定值。