We examined the retinotopic mapping of the visual world in the primary visual cortex of the marmoset monkey using differential optical imaging. Two sets of complementary stripe-like locations were visually stimulated in turn. Their difference depicts the cortical representations of continuous bands of visual space. By rotating the sets of stripe-like locations it is possible to map different spatial axes. Analogous to the macaque we found that the V1/V2 border represented the vertical meridian, while horizontal, 45-, and 135-degree angled stripes of space were also represented in a continuous manner. We developed a new automatic method of calculating local measures of cortical magnification from our optical retinotopic maps. Using this method we found no evidence of any local anisotropies in cortical representation. Overall our results indicate that space is mapped isotropically in the primary visual cortex of the common marmoset.