To provide a liquid state detection device capable of determining the stationary state of liquid by using an output acquired separately in a process for detecting a concentration value by carrying a current in a heating resistor.

A concentration conversion value Cn is determined from a differential value ΔVmn between each voltage value of the heating resister measured after start of energization (after 10 msec) and after elapse of a fixed time (after 700 msec). A concentration conversion value Cp is determined from a differential value ΔVmp between a voltage value measured after a determination time (after 500 msec) shorter than elapse of the fixed time and the voltage value after start of energization, and a differential value between both values is calculated as a concentration fluctuation width (S102). If the value is larger than a threshold K determined beforehand as a reference of the stationary state, it is determined that urea aqueous solution is not in the stationary state (S111). In the case out of the stationary state, even if an abnormal state of the urea aqueous solution is detected, reliability of determination is heightened by increasing the opportunity (the number of times) of detection of the abnormal state until being determined to be in the abnormal state.

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