The present invention provides an image coding apparatus and an image coding program that execute quantization control so that a generating bit is made close to a target bit. The image coding apparatus according to the present invention includes a generated bit measurement unit, a target bit setting unit, a residual bit computing unit for computing a residual value between the generated bit and the target bit, a remaining video buffer capacity measurement unit, and a quantization parameter computing unit for computing a quantization parameter to set the same to the quantization unit. The quantization parameter computing unit computes a quantization parameter for next image data to be encoded on the basis of at least one of the residual value computed and the remaining video buffer capacity measured.