We present comprehensive multi-wavelength observations toward IRAS 17589-2312 which is located near the supernova remnant (SNR) W28. A cold dust condensation (W28MM) is detected using an IRAM 1.3mm continuum observation. Two bipolar outflows and water maser are also detected, implying that W28MM is at an early stage of massive star formation. Spitzer infrared images reveal, within the W28MM dust core, seven infrared sources that are Class 0/I protostars based on the Spitzer colors, indicating that the core is a massive protostellar cluster. The model fitting of the spectral energy distribution of the infrared protostars show the two most massive stars have similar masses of 8-11 solar mass. The protostellar cluster appears in a long filamentary infrared-dark-cloud hich extends through the young HII region of the Triffid Nebula, the dust core of W28MM, and the SNR of W28. We discuss initial mass function of the massive protocluster, the star formation processes of the massive stars, and the possibilities of shock triggering star formation along the CO velocity structures of the clouds.