A block decoding method for a two-dimensional code, comprising: storing a received two-dimensional code image in an image data backup register; binarizing the received two-dimensional code image based on a gray-scale value of a pixel; searching for a boundary line of the two-dimensional code image based on a position detection pattern; searching for a version number of the two-dimensional code image; characterized by comprising: segmenting the two-dimensional code image into regions based on the boundary line of the two-dimensional code image and a straight line where a boundary line of the position detection pattern is located; calculating the number of bits in each of the regions based on the position detection pattern and the version number; segmenting each of the regions into bit regions each of which corresponds to one bit data, based on deformation amount of the position detection pattern; re-acquiring the received two-dimensional code image stored in the image data backup register; calculating an average gray-scale value of all the pixels in the bit region as a gray-scale value of the bit region; calculating a gray-scale threshold of each of the bit regions based on the gray-scale value of the bit region using the Otsu method; binarizing the bit region based on the gray-scale threshold so as to obtain a binarized two-dimensional code image; and decoding the binarized two-dimensional code image. storing a received two-dimensional code image in an image data backup register; binarizing the received two-dimensional code image based on a gray-scale value of a pixel; searching for a boundary line of the two-dimensional code image based on a position detection pattern; searching for a version number of the two-dimensional code image; characterized by comprising: segmenting the two-dimensional code image into regions based on the boundary line of the two-dimensional code image and a straight line where a boundary line of the position detection pattern is located; calculating the number of bits in each of the regions based on the position detection pattern and the version number; segmenting each of the regions into bit regions each of which corresponds to one bit data, based on deformation amount of the position detection pattern; re-acquiring the received two-dimensional code image stored in the image data backup register; calculating an average gray-scale value of all the pixels in the bit region as a gray-scale value of the bit region; calculating a gray-scale threshold of each of the bit regions based on the gray-scale value of the bit region using the Otsu method; binarizing the bit region based on the gray-scale threshold so as to obtain a binarized two-dimensional code image; and decoding the binarized two-dimensional code image. segmenting the two-dimensional code image into regions based on the boundary line of the two-dimensional code image and a straight line where a boundary line of the position detection pattern is located; calculating the number of bits in each of the regions based on the position detection pattern and the version number; segmenting each of the regions into bit regions each of which corresponds to one bit data, based on deformation amount of the position detection pattern; re-acquiring the received two-dimensional code image stored in the image data backup register; calculating an average gray-scale value of all the pixels in the bit region as a gray-scale value of the bit region; calculating a gray-scale threshold of each of the bit regions based on the gray-scale value of the bit region using the Otsu method; binarizing the bit region based on the gray-scale threshold so as to obtain a binarized two-dimensional code image; and decoding the binarized two-dimensional code image.