A position transmission device adapted to be installed in a vehicle, comprising: abnormality detection means that outputs an abnormality detection signal when an abnormality state of the vehicle is detected based on acceleration variation occurred in the vehicle; an alarm device that responds to the abnormality detection signal and gives an alarm, and transmission means that transmits position information of the vehicle to a predetermined entity to be notified; characterised in that the position transmission device also comprises mode switch means provided with the following action modes: an ignition ON mode when the state of the ignition switch of the vehicle is ON, in which - the transmission means transmits the position information at a third period, and - the abnormality detection section and the alarm device are switched off; and a sleep mode when the state of the ignition switch of the vehicle is OFF, in which - the transmission means transmits the position information at a first period, and - the alarm device is driven whenever the abnormality detection signal is outputted; and a truck mode when the state of the ignition switch of the vehicle is OFF, and when predetermined operation means out of the operation means that control the actions of the vehicle are operated in a predetermined operation pattern in which - the transmission means transmits the position information at a second period shorter than the first period but longer than the third period, and - the position transmission device responds to the abnormality detection signal by lowering the output of the alarm device below the level of output in the sleep mode; wherein the mode switch means switches the action mode to the ignition ON mode when the ignition switch of the vehicle is switched ON in each of the sleep and truck mode; wherein the mode switch means comprises a mode switching section which switches between the ignition ON mode and the sleep mode or the truck mode according to whether the ignition switch is ON or OFF. abnormality detection means that outputs an abnormality detection signal when an abnormality state of the vehicle is detected based on acceleration variation occurred in the vehicle; an alarm device that responds to the abnormality detection signal and gives an alarm, and transmission means that transmits position information of the vehicle to a predetermined entity to be notified; an ignition ON mode when the state of the ignition switch of the vehicle is ON, in which - the transmission means transmits the position information at a third period, and - the abnormality detection section and the alarm device are switched off; and - the transmission means transmits the position information at a third period, and - the abnormality detection section and the alarm device are switched off; and a sleep mode when the state of the ignition switch of the vehicle is OFF, in which - the transmission means transmits the position information at a first period, and - the alarm device is driven whenever the abnormality detection signal is outputted; and - the transmission means transmits the position information at a first period, and - the alarm device is driven whenever the abnormality detection signal is outputted; and a truck mode when the state of the ignition switch of the vehicle is OFF, and when predetermined operation means out of the operation means that control the actions of the vehicle are operated in a predetermined operation pattern in which - the transmission means transmits the position information at a second period shorter than the first period but longer than the third period, and - the position transmission device responds to the abnormality detection signal by lowering the output of the alarm device below the level of output in the sleep mode; - the transmission means transmits the position information at a second period shorter than the first period but longer than the third period, and - the position transmission device responds to the abnormality detection signal by lowering the output of the alarm device below the level of output in the sleep mode; wherein the mode switch means switches the action mode to the ignition ON mode when the ignition switch of the vehicle is switched ON in each of the sleep and truck mode; wherein the mode switch means comprises a mode switching section which switches between the ignition ON mode and the sleep mode or the truck mode according to whether the ignition switch is ON or OFF.