Provided is a method for improving efficiency of heat transmission that enables improving the efficiency of heat transmission by steam in a steam system at a pH of less than 7. A method for improving the efficiency of heat transmission by steam, wherein, in a step of introducing steam into a heat exchanger to heat an object to be heated or a step of contacting the steam with a cooling body to liquefy the steam, a sarcosine compound is allowed to be present in the steam system at a pH of less than 7. As the sarcosine compound, a long-chain sarcosine compound represented by the following formula (I) is preferable. R.sup.1C(O)N(CH.sub.3)(CH.sub.2).sub.nCOOR.sup.2 . . . (I) In formula (I), R.sup.1 is an unsaturated or saturated linear or branched hydrocarbon group having 7 to 24 carbon atoms, n is an integer of 0 to 2, and R.sup.2 is a hydrogen atom or a salt-forming group.