A thermal fixing device and an image forming apparatus having a thermal
fixing device being capable of executing a fixing operation rapidly for
printing mediums of different sizes with a stable fixing temperature at
any time without causing a hot offset is provided. In a first halogen lamp
A and a second halogen lamp B, thermal density (A1) of a first heat region
corresponding to a first region HX that a small size paper 3a contacts and
thermal density (B1) of a first heat region BX, and thermal density (A2)
of a second heat region AY corresponding to a second region HY that a
large size paper 3b contacts and thermal density (B2) of a second heat
region BY are set so as to satisfy conditions that A1>A2 and B1
