The invention discloses a state detection device applied to a mobile terminal and a mobile terminal, a technical effect of performing detection on the service state of the mobile terminal is realized, and the mobile terminal is enabled to improve a waterproof protection effect and an antenna switching effect based on a service state detection result when designing functions such as waterproof protection and antenna switching. The state detection device is characterized in that a primary antenna radiator is excited by a primary antenna signal source to realize self resonance and radiation in a set frequency band, and a metal secondary antenna radiator is enabled to be excited by the primary antenna radiator to generate secondary radiation in the set frequency band; a secondary antenna radiation signal coupler acquires an antenna signal radiated by the metal secondary antenna radiator, a signal receiver receives the antenna signal and judges whether the radiation frequency thereof is the radiation frequency of the set frequency band or not; and an antenna state detection module generates a state detection result of the mobile terminal according to a judgment result of the signal receiver. Operations such as waterproof protection and antenna switching can be executed according to state variations after the state of the mobile terminal is acquired.