An image coding apparatus configured to divide an image into one or more slices each including a plurality of blocks and to code each slice on a block-by-block basis includes a first coding unit configured to code blocks included in a first portion of the slice, and a second coding unit configured to code blocks included in a second portion of the slice, wherein, when the second coding unit codes an initial block in the second portion, the second coding unit codes the initial included in the second portion by referring to a first quantization parameter provided to the slice as an initial value and referred to by the first coding unit when the first coding units codes the initial block in the first portion.