A WAP (Wireless Application Protocol) analyzer located on a transmission line between communication apparatuses using WAP. A WAP packet includes at least one WTP-PDU (Wireless Transaction Protocol-Protocol Data Unit). The WAP analyzer comprising, database (16) for storing state-transition specification data that define a state-transition with a cause-and-effect relationship between WTP-PDUs, states of a WTP layer, primitives between the WTP layer and WSP (Wireless Session Protocol) layer, and states of the WSP layer, based on WAP specification, means (11) for extracting the WTP-PDUs from the WAP packets, and means (13) for estimating the state-transition of the WTP layer and the WSP layer, to the apparatus that received one of the WTP-PDUs and subsequently sent other of the WTP-PDUs, for each pair of a sender and a receiver.