A tubular heater for heating liquid is a heater used for heating various liquids. A tubular heater consists of a nichrome wire heating element enclosed in a metal sheath, and various shapes are available. Products are available that not only heat water or oil, but also chemicals that tend to cause corrosion or liquids that react badly to metal ions. Products equipped with an overheating prevention function are also available. Another type is the immersion heater that is simply inserted into the liquid directly to heat the liquid.