Methods and systems of measuring communication quality are provided, by which various types of communication quality measurements can be flexibly performed as the measurement condition can be set or changed easily and optionally, while load of processing in the communication terminal apparatus can be suppressed. Measurement condition for measuring communication quality is delivered to a communication terminal apparatus capable of communicating via a mobile communication network and a communication with the communication terminal apparatus via the mobile communication network is performed at a predetermined timing that satisfies the measurement condition. Then, at least one of terminal-side measurement data including terminal-status log information and network-side measurement data including terminal-existing base-station quality information corresponding to communication corresponding to the predetermined timing which are recorded in the communication terminal apparatus is acquired, and an index value of communication quality in communication via the mobile communication network is calculated based on at least one of the terminal-side measurement data and the network-side measurement data.