A biological signal drawing apparatus draws biological signals as drawing points in time series. The biological signal drawing apparatus includes: a thinner performing a thinning process to thin a first number of the drawing points corresponding to the biological signals sampled in each pixel zone, to obtain a second number of the drawing points for each pixel zone, the second number being smaller than the first number； a calculator, after the thinning process is performed, calculating a parameter based on at least one difference of values of adjacent two of the drawing points included in a group that includes: a first drawing point being a center in time series in the group and having a first value； and at least one second drawing point preceding or succeeding the first drawing point in time series and having a second value； and a processor performing a process of: performing a weighted moving average calculation using the first value, the second value and the calculated parameter, to obtain a third value； and replacing the first value with the third value.
