Centrifugal deployment dynamics of hexagonal membranes stowed with spiral folding are investigated. The centrifugal deployment has a possibility of unfolding large membranes without using extendable masts. Understanding and predicting the deployment dynamics are important to realize large membrane space structures. In this paper, deployment experiments of hexagonal membranes with coarse and fine spiral folding patterns are conducted in vacuum under gravity. Numerical simulations of the centrifugal deployments are also performed employing spring-mass system which models in-plane stiffness of thin membranes and enables fast numerical analysis. Additional modelings taking accounts of buckling, creases, air drag and damping are applied to the spring-mass system model. The experimental and numerical results are compared to examine the characteristics of the deployment dynamics and the validity of the numerical simulation.