Fixing device and image forming apparatus

A fixing device comprising:

• a fixing belt that is endless;
• and
• a heating section facing an inner peripheral surface of the fixing belt, wherein,
• the heating section includes:
• a heater which applies heat to the fixing belt;
• and
• a heater holding member which holds the heater,
• the heater holding member has:
• a main body portion;
• and
• a plurality of ridges which regulate a shape of the fixing belt,
• the ridges protrude from the main body portion,
• the ridges include:
• a plurality of first ridges disposed on a central portion of the main body portion in a width direction of the fixing belt;
• and
• a plurality of second ridges disposed in an area of the main body portion at least partially extending, in the width direction of the fixing belt, from the central portion to each of opposite ends of the main body portion,
• the first ridges are disposed separated at a first interval,
• the second ridges are disposed separated at a second interval, and
• the first interval is smaller than the second interval.