The present invention is a peritoneal function testing method characterized by using a ratio MTACun/MTACc calculated using MTACun and MTACc as an index for a peritoneal function test, where MTACun is an overall mass transfer-area coefficient for urea nitrogen and MTACc is an overall mass transfer-area coefficient for creatinine. The use of MTACun/c of the present invention in this way enables examination of the future peritoneal function of a patient (a mechanism of deterioration in peritoneal function). To be specific, MTACun and MTACc can be obtained by computing Pyle-Popovich model. In addition, the peritoneal function testing method may further calculate a permeability coefficient for cell pores (LPSC) and an overall permeability coefficient (LPS) from Three-Pore Theory model while obtaining a ratio LPSC/LPS calculated using the LPSC and the LPS, and may use the LPSC/LPS ratio and the MTACun/MTACc ratio as indexes for the peritoneal function test.
