To provide a coding device for coding data in high speed with a desired compression rate.

An image processing device (coding device) 2 is designed to monitor code amount in every line, and to restart a coding process of a noticed line after adding a reference position when the code amount exceeds standard code amount. Thus the image processing device 2 can obtain the desired compression rate after adding the reference position (prediction method) relating to a line which is hard to be compressed by a default predictive coding process while monitoring the code amount in every line, and can perform coding in high speed with fewer process loads using only the default prediction method relating to partial pieces of data which can be easily compressed.