Parity inspection matrix creation method, encoding device and recording/playback device

According to an embodiment, in a parity inspection matrix creation method, N column vectors within a mask matrix are all mutually different. A partial matrix of L consecutive rows arbitrarily extracted from the mask matrix contains B 1 first correction rows and B i ith correction rows. Each row weight of the B 1 first correction rows is 1. The B 1 first correction rows are provided with a total of one or more '1's in each of A 1 first correction columns. Each row weight of the B i ith correction rows is 2 or more. Each of the B i ith correction rows is provided with a total of one or more '1's in A i-1 i-1th correction columns. Each of the B i ith correction rows is provided with a '1' in one of A i ith correction columns that are contained in a column group that excludes the columns from the first correction column to the i-1th correction column. The B i ith correction rows are provided with a total of one or more '1's in each of the A i ith correction columns. The summation from A 1 to A I is equal to L .