To provide a work machine operation assistance device which enables setting a manipulation gain appropriate for a skill level and habits of an operator and/or actual work contents. The work machine operation assistance device according to the present invention includes : a manipulation gain storage section storing a manipulation gain; a manipulated variable detection section detecting a manipulated variable of the operating device; a time integration section adding up time that the operating device is operated; a manipulated-variable frequency arithmetic section computing a manipulated-variable frequency of the operating device; a manipulated-variable frequency criterion setting section presetting a criterion value for the manipulated-variable frequency; a manipulation gain update arithmetic section performing a computation to update the manipulation gain; a manipulation gain display section displaying a result of the manipulation gain computed; and a manipulation gain update selection section to select whether or not an update to the manipulation gain displayed on the manipulation gain display section is performed.