An image forming apparatus for a printer forms images by injecting inks on a printing paper being fed on a feeding path. The image forming apparatus comprises a head holder surface provided on the feeding path with being opposed to a surface of the feeding path and a plurality of ink heads for injecting inks from injection ports thereof. Here, the injection ports of the plurality of ink heads are projected outward from the head holder surface. The image forming apparatus can achieve further downsizing and multifunctional capability and improve quality of higher pixelated printed images. In addition, the image forming apparatus can prevent negative effects such as ink injection failures or defacement of printed matters due to ink mists made on injecting ink.