A node apparatus and an adjusting method of a quantity of nodes for a sensor network and a tangible machine-readable medium thereof are provided. The sensor network comprises a plurality of groups, wherein each group has a plurality of nodes. For each group, one of the nodes is set to be a gate node, and each node within the group transmits at least one data of itself to the corresponded gate node. Each gate node calculates a data aggregation time based on a data length per unit time of received data and a predetermined packet length, so that each gate node is able to adjust the quantity of nodes within the group thereof accordingly.