1. An image coding method for coding image data on a block-by-block basis, the image coding method comprising: segmenting a block including coefficients of frequency components, into groups corresponding to frequency ranges based on types of the coefficients, and determining a context corresponding to each of the groups; performing, for each of the coefficients, binary arithmetic coding on the coefficient according to a probability information item corresponding to the context, the context being corresponding to the group having the coefficient; and updating, for each of probability information items, the probability information item corresponding to the context, based on the coefficient included in the group corresponding to the context, wherein in the segmenting, the block is segmented into the groups with various numbers of coefficients.