Provided are a controller and a control method for a homogeneous charge compression ignition engine, which are capable of obtaining a highly efficient and stable combustion state over a wide range of load condition. A correction factor computing section executes combustion control with an excess air ratio smaller than approximately 3 when a predetermined condition is satisfied and computes a correction factor for correcting deviations between execution values of valve-opening timings and valve-opening periods of an intake valve and an exhaust valve and basic valve-opening timings and basic valve-opening periods of the intake valve and the exhaust valve which are previously determined for each operation condition, based on a timing at which an ion current becomes maximum detected by a combustion-timing detection section, in the combustion control with the excess air ratio smaller than approximately 3.