Reliability of an electronic package is predicted based on material type, shape and dimensions of the package and conditions for assessment thereof, and a modeling unit creates a simulation model based thereon. An executing unit uses the simulation model to execute a simulation under designated conditions and results of the simulation are stored in a database. The stored simulation is assessed according to the assessment criteria and the assessment results are stored in a database. A generating unit generates, as an assessment expression, an approximate expression which infers the results of assessment from the inputted parameters, on the assumption that a predetermined amount of results of assessment is preserved. An assessment predicting unit outputs the results of an assessment of a package in which an assessment expression has already been established, by using the assessment expression.