In vitro three dimensional (3D) cancer models were developed to observe the invasive capacity of melanoma cell spheroids co-cultured with the vascular-formed endothelial cell network. An array-like multicellular pattern of mouse melanoma cell line B16F1 was developed by magnetic cell labeling using a pin-holder device for allocation of magnetic force. When the B16F1 patterned together with a vascular network of human umbilical vein epithelial cells (HUVEC), spreading and progression were observed along the HUVEC network. The B16F1 cells over 80 µm distance from HUVEC remain in a compact spheroid shape, while B16F1 in the proximity of HUVEC aggressively changed their morphology and migrated. The mRNA expression levels of IL-6, MDR-1 and MMP-9 in B16F1 increased along with the distance the HUVEC network, and these expressions were increased by 5, 3 and 2-fold in the B16F1 close to HUVEC (within 80 µm distance) as compared to that far from HUVEC (over 80 µm distance). Our results clearly show that malignancy of tumor cells is enhanced in proximity to vascular endothelial cells and leads to intravasation.